Chapter 3 zero visibility

Deep sea wreck diving is one of the most dangerous sports in the world.The few who survived also suffered from the unpredictable and ubiquitous joint blows to the brain from nature, the biological world, diving equipment, their own intuition and exploration targets, constantly disintegrating their will.Many divers died at the bottom of the sea, and when their bodies were found in the wreck, it was found that they still had enough oxygen to help them return to the surface.Instead of suffocating, they lose the ability to judge how to live. Public awareness of the sport is very limited and it is very different from resort diving with unpredictable safety factors.Of the 20 million certified divers worldwide, deep water wreck divers represent a very small percentage.But their accident rate is very high. Because of this, almost all diving sports enthusiasts are only willing to stay in the shallow water of the tropics and dive with others to ensure safety. They are usually only satisfied with enjoying the beautiful scenery of the seabed.Only a few hundred of the 10 million certified divers in the United States have ventured into the deep sea to find shipwrecks.For this small group of people, what matters is not whether they fear death, but whether they can bear it.A diver who has been engaged in deep-sea wreck diving for a long time usually encounters three situations: he may have a brush with death, he may witness the death of others, or he may be buried in the sea himself.Sometimes it is difficult to say which of these three outcomes is the worst.

On the other hand, deep sea wreck diving is also a special sport.Since this sport challenges people's most primitive instincts—breathing, vision, and escaping from danger—laymen don't need to carry diving equipment to experience it in person, and only need to imagine to understand the dangers of this sport.After knowing these dangers, you can understand and feel the stories of wreck divers, and you can understand why excellent divers are buried in the bottom of the sea, and why most people don't dive 60 miles off the coast with the numbers provided by fishermen. 200 feet deep in no man's land to find shipwrecks.

A diver who is still alive is bound to encounter two main dangers.First, in water deeper than 66 feet, his judgment and motor skills are greatly impaired, a symptom commonly known as nitrogen narcosis.If he dived deeper, the symptoms of nitrogen narcosis would be more pronounced.And to find the best underwater wrecks, the depth of diving must exceed 100 feet, at this depth, the diver's ability will be severely impaired.But the diver must ensure the accuracy of actions and decisions, because this directly determines whether he can survive. Secondly, once something unexpected happened, he couldn't swim out of the water immediately.Divers who spend time in deep water must slowly return to the surface, stopping at intervals to allow their bodies to adjust to the reduced air pressure.Even if it feels like you're going to suffocate, you have to do it.If a diver panics too much and rushes to surface, there is a high risk of decompression sickness.Severe decompression sickness can lead to permanent disability, paralysis and even death.Divers who have witnessed the excruciating symptoms of decompression sickness swear they don't rush to the surface without decompression even if they drown at the bottom of the ocean.

In addition to nitrogen narcosis and decompression sickness, deep-sea wreck divers face countless difficulties and dangers.Nitrogen narcosis and decompression sickness are both phenomena caused by changes in pressure.When throwing a Frisbee at the beach or riding a bus, we're in an environment with standard atmospheric pressure, or an atmospheric pressure of 14.7 pounds per square inch.In an environment of standard atmospheric pressure, the feeling of being alive is normal.The air we breathe at sea level is composed of 21% oxygen and 79% nitrogen, and the pressure formed in the lungs is equivalent to one atmosphere.Oxygen satisfies the needs of our blood and body tissues, while the inert gas nitrogen does little.

In water, all situations are different.For every 33 feet below the surface, one atmosphere of pressure increases.A diver playing with seahorses at a depth of 33 feet is in two atmospheres, or twice the air pressure at the surface.This change is hardly noticeable.But the amount of air he inhales from the cylinder varies.The air he inhaled was still composed of oxygen molecules and nitrogen molecules in a ratio of 21:79, but now twice as many molecules entered his lungs with each breath he inhaled as when he was on land.Three times as many molecules are inhaled at three atmospheres, and so on.

When a diver breathes underwater, excess nitrogen molecules inhaled into the lungs don't stay put as they do on land.Instead, nitrogen molecules dissolve into the blood and travel with the blood to every tissue in the body—muscles, joints, brain, spine, and so on.The longer a diver stays underwater and the deeper he dives, the more nitrogen molecules accumulate in his tissues. At a depth of three atmospheres, or 66 feet, the molecular nitrogen buildup in most divers kicks in.This is what is commonly referred to as nitrogen narcosis symptoms.Some people think that the symptoms are similar to the symptoms of drunkenness, others think that the effect of narcotic drugs is about to wear off, and others think that they are like the reaction after inhaling ether or laughing gas.The symptoms of diving in shallow seas are relatively mild. Generally, there will be slow judgment, weakened motor function, reduced finger flexibility, narrow vision, and high emotions.As the depth increases, the reaction will increase accordingly, and most divers will feel weak at a depth of 130 feet.Some are so numb that they can barely do very simple things like knotting a rope; others are sluggish and have to constantly remind themselves of what they already know.If the depth goes to 170 or 180 feet, the diver will start to hallucinate, he will feel that the lobster is waving to him by his name, or giving him wrong advice.Many people have heard the "Jungle Drum," the deafening drumbeat that is actually the pulse beating in their own ears.Some people just hear a buzzing sound, like an alarm clock under their pillow.After reaching a depth of 200 feet, nitrous narcosis can distort how you really feel, such as fear, happiness, sadness, excitement, or disappointment.You'll feel like an insignificant problem—losing a dive knife or encountering a bit of sand—is an endless catastrophe that builds up into a feeling of extreme dread.Serious problems—running out of air or missing a mooring line—feel like trivial ones.All is compounded by impaired judgment, emotion, and motor skills in a harsh environment such as a deep-sea wreck expedition.

Nitrogen inhaled by divers creates another problem.As the depth and length of the dive increase, more and more nitrogen molecules will accumulate in the diver's body tissues.This is not a problem on short dives in shallow water.But during long dives at depth, nitrogen molecules that build up in body tissues are released back into the bloodstream during the ascent.The speed of release directly determines whether a diver will suffer from decompression sickness, or even cause death. If the diver ascends slowly and the air pressure gradually decreases, the accumulated nitrogen is expelled from the tissues in the form of tiny bubbles.We can understand this phenomenon by observing the process of opening a soda bottle.If you slowly reduce the pressure in the bottle, the bubbles in the soda will be very small.The size of the bubble volume is a critical factor.Only when the nitrogen bubbles in the diver's body are very small can they be effectively returned to the lungs through the blood and then out of the body through normal breathing, which is what divers hope.

However, if a diver ascends rapidly, the atmospheric pressure around him drops rapidly.This causes the nitrogen gas that builds up in the diver's tissues to form large volumes of bubbles, like what you see when you quickly unscrew the cap of a soda bottle.Large volumes of nitrogen gas bubbles are the deadly enemy of deep sea divers.Large volumes of air bubbles that appear outside blood vessels will compress body tissues and impede blood circulation.If it occurs near a joint or nerve it can cause weeks or even lifelong pain.If air bubbles develop in the spine or brain, they can cause paralysis or death.If too many large air bubbles return to the lungs at the same time, lung function ceases, causing symptoms of asphyxia, which may cause the diver to stop breathing.If too many large air bubbles enter the arterial system, divers can develop pulmonary barotrauma, or air embolism, which can cause blindness, fainting or death.

In order to ensure a slow ascent speed and the formation of tiny nitrogen bubbles, deep-sea divers will deliberately stop at a predetermined depth so that these bubbles can be smoothly expelled from the body.This is the so-called "decompression stop", and the distance between each stop has been accurately calculated by scientists.If you dive for 25 minutes at a depth of 200 feet, the time required to return to the surface is an hour.Start at 40 feet for 5 minutes, slowly ascend to 30 feet for 10 minutes, 20 feet for 14 minutes, and 10 feet for 25 minutes.The amount of time you spend on decompression is determined by the depth and length of the dive—the longer and deeper you are, the more time you spend on decompression.This is one of the reasons why wreck divers never spend an hour underwater.As much as nine hours of decompression time is required for a two-hour dive.

If you plotted a tree diagram of the dangers faced by deep-sea wreck divers, nitrogen narcosis and decompression sickness would be at the top of the tree.Not all divers dare to go out to sea for wreck exploration unless he has enough courage to face these dangers. Atlantic divers on the northeast coast go out to sea on wreck expeditions by chartering a dive charter boat.Although many divers have their own recreational boats, such boats simply cannot withstand the stormy waves of the Atlantic Ocean.The length of the diving charter boat is generally more than 35 feet, and the hull is specially designed to resist the wind and waves at sea.Generally speaking, customers who rent a boat to dive dive twice a day, but between the two dives, there must be a period of time to discharge the nitrogen in the body.Therefore, a diving charter boat usually goes out to sea for a day or a day and a night at a time.

Good divers make a detailed plan before boarding a boat.A few days or even a week before the expedition, he would conceive various ideas about the wreck, study the deck plan of the wreck, memorize the outline of the hull, determine the work area, formulate reasonable goals, and then construct corresponding countermeasures based on the goals.Divers believe that orienting themselves on the ocean floor is the number one factor in safely and successfully boarding a wreck.Many divers are reluctant to search a wreck aimlessly.Some people have done this, but these people usually die at sea and never come back.Good divers believe in a well-thought-out plan.They usually have a clear idea of ​​the wrecks they are exploring and where they are going to explore before they dive, so that they can prepare for possible surprises.And in the depths of the Atlantic, anything can be an accident. Good equipment is a diver's closest companion.It can assist divers to enter the restricted area where no one is, and set up a powerful barrier against natural forces in front of divers.When the diver puts on his 175-pound wetsuit, he looks like a cross between a modern sculpture and an alien from a 1950s movie.After the equipment is completed, the diver can only stagger forward at a cumbersome pace, but the diving suit is a symbol of life to him.If any part of the equipment fails, his life is in danger.During the diving process, divers have to wear diving equipment worth thousands of dollars: flashlights, headlights, flashlights, guide ropes, hammers, crowbars, diving knives, masks, fins, fin buckles, buoyancy regulators, breathing adjustments Snorkel, compass, backpack for wreck items, lifting bag for bringing items out of the water, buoy markers for popping out of the water in an emergency, clips, rulers, dials, writing slates, waterproofing Tags, rubber gloves, diving caps, diving watches, diving belts, ankle sandbags, etc.Then he will prepare some spare equipment.He puts on an expensive, warm dry suit and two expedition underwear underneath.He will carry two cylinders, one is not enough.All these devices are indispensable. Once the ship is close to the target, the captain uses the nautical equipment to position the ship over the position indicated by the "number", or as close as possible to the wreck's position.His helpers—usually two or three divers working on the boat—would find footing on the smooth foredeck before grabbing the anchor's fluke and chain.The diving boats are equipped with steel multi-claw anchors, usually with four to five claws, which look less like the two-claw anchors tattooed on the upper arms of sailors in the past, and more like the tools used by Batman to climb buildings.The ship's end of the anchor is connected to a 15-foot-long iron chain, followed by hundreds of feet of nylon rope.After the captain gives the order, the assistant will drop the anchor, hoping to hook the wreck. Precisely lowering the anchor is a critical step.The anchor rope not only plays a role in keeping the hull still, but also serves as a guide rope for divers. The diver will search for the anchor rope to find the sunken ship, and more importantly, he will return to the diving boat through the anchor rope.Divers can't just jump off a boat, fall into the ocean, and land right on a wreck.After he entered the water, the dive boat may have drifted hundreds of feet with the current and was no longer above the wreck.Even if the diving boat is still above the sunken ship, there is no anchor rope to guide the direction. After the diver jumps into the sea, it will fluctuate with the current in the sea, and it is completely impossible to grasp the direction.Currents could have pushed him hundreds of feet away from the wreck.Visibility may be less than ten inches on the dark ocean floor deep in the Atlantic Ocean, and divers may not be able to spot a wreck after landing even a few feet from it.Even with good sea bottom visibility, say 40 feet, a diver who freedives to the bottom without a mooring line will not see the wreck if he lands 45 feet from the wreck.In this case, he had to guess a direction and look for it, and if his guess was wrong, he would wander around the bottom of the ocean, possibly lost.Only by following the anchor line can divers find the location of the wreck. What is more important is to find the anchor line and return to the dive boat.If the diver cannot find the anchor line, he has to surface under his own power while decompressing.This free ascent is likely to be dangerous.A diver has to decompress—a process that takes at least an hour, depending on the length and depth of the dive—and without an anchor line to stabilize his body, it is difficult for him to know the exact depth he needs to decompress, eventually leading to decompression sick.But decompression sickness is just the beginning.Without an anchor line, the diver would drift with the current in the sea.Even if he was able to start the ascent from directly under the dive boat, after an hour of decompression in a current traveling at two knots—about 2 miles per hour—he would have surfaced at least two miles from the dive boat. .The distance between the two prevented him from seeing the dive boat at all.Even if he saw the dive boat, he couldn't swim to it.No diver carrying hundreds of pounds of equipment in the upstream would be able to overcome these two obstacles and swim near the dive boat.He doesn't drown immediately because he has buoyancy equipment and he has air in his wetsuit and buoyancy adjustment device to help him stay afloat.But the misery was not far away, and he knew he would die of hypothermia after only a few hours in the frigid Atlantic waters.He knew very well that sharks in the sea might attack divers floating in the sea at any time.And even if he survives 24 hours, the cuffs of the diving suit will be softened by the salt water and start to leak air, and seawater will seep into the diving suit.As the temperature slowly dropped, he knew that those on board would not realize that he had surfaced.They might have thought he was lost at the bottom of the sea or attacked by a shark, but they could never be sure what happened to him because it was almost impossible to see him floating among the white waves of the Atlantic Ocean.No one knew he was still alive.There is nothing worse than this for a diver lost in the sea. The anchor line is a diver's lifeline, so the anchor line is not just lowered and done.The anchor line will sway with the seabed current and cannot hook the sunken ship.Therefore the anchor must be securely fastened to the wreck.This work is to be done by an assistant.They would dive to the bottom of the sea and tie anchor lines to the wreck.After the tying is complete, the assistant will release several white foam water cups as a signal to tell the captain and divers that the anchor line has been tied tightly.On dive charters in the Atlantic, a white glass means it's time to dive. After the diver saw the white water glass, he opened his bag and began to prepare his equipment.He knows exactly how to install each piece of equipment efficiently: every belt is adjusted to the optimum length, the position of every tool is expertly calculated, and everything fits together perfectly.Every movement of his is very familiar.He basically does not need help from others.If other divers come to assist him, he usually refuses, saying, "No thanks," or "Don't touch me."He prefers a ten-dollar dive knife to a hundred-dollar dive knife so that when he loses his dive knife at the bottom of the ocean, he won't be overly frustrated by the stress of narcosis and risk his life Searching hard at the bottom of the sea.He doesn't care if the wetsuit is clean or not, and he'll often have patches, stickers, or drawings on it to commemorate past adventures.They will not choose neon wetsuits, only beginners will choose this hue.When equipped, they look as perfect as the engine of a German car. The fully-equipped diver weighs 350 pounds per foot, with what appear to be bulges of muscle, like a rubber Sasquatch.Finally, he would spend a few seconds clumsily lumbering across the slick foredeck, at which point he would likely slip and fall to the ground if a wave suddenly hit him.He will spend 25 minutes on two cylinders on the wreck at a depth of 200 feet, before having to decompress for an hour before rising to the surface. Once in the water, the diver no longer feels the weight of the cylinder.On the contrary, the cylinder seemed to float away from him at any moment.He grabbed the rope that connected the bow to the anchor chain and opened the valve on the wetsuit to let out a little air so he could reduce his buoyancy just below the surface.He climbed the rope to the hawse and let out a little more air so that he began to sink slowly. Now the diver embarks on his journey to explore the wreck.Most divers explore wrecks alone.In the sport of recreational diving, diving is usually done in teams of two.The divers are paired with each other and are always available to help each other.In clear shallow water, diving with a partner is the most ideal method.They can share the air when diving equipment fails, assist a fellow mate in difficulty to surface, or assist a fellow entangled in a fishing line to get out.Having a companion with you can make you feel comfortable and reassured.But in the depths of the Atlantic, even a well-meaning diver can threaten the life of his fellow divers.If a diver squeezes into the cramped hold of a sunken ship to rescue his partner, he is likely to be trapped himself, and he may block the view of the cabin so that neither can find their way out.If a diver tries to share oxygen with a panicked companion, he also faces life-threatening danger.A diver who suffocates at 200 feet on the ocean floor sees his fellow diver as a lifeline, and he may kill him to get his oxygen.A terrified diver would lash out at his rescue partner with a dive knife, snatch the regulator from his mouth, and then frantically dash to the surface without decompression. In the depths of the ocean, even seeing other divers in distress can be dangerous.At a depth of 200 feet under the sea, divers are already highly stressed by nitrogen narcosis.If he was confronted by a diver who thought he was about to die, he would mistake those desperate eyes for his own.Through the painful expression of his companion, he may see the possibility of this pain appearing in himself.Under such circumstances, he either panicked or did everything in his power to rescue his trapped companions.Either way, his life went from safe to dangerous.But that doesn't mean divers can't go on wreck expeditions in pairs -- on the contrary, they often do.But only for good divers who don't depend on others for security.Their philosophy is to deal with problems calmly and independently, and to know how to rescue themselves. The diver descends to the bottom of the sea along the anchor line with little effort.Generally, it takes about two to four minutes to reach a depth of 200 feet on the sea floor.During the descent, he felt almost no gravity, like an astronaut in the sea.During the first few feet of descent, the world before the diver's eyes is blue and clear.He could see yellow dots dotted on the cellophane-like sea above his head.In the shallow sea, divers will not see much marine life, only individual tuna and dolphins may be attracted by divers' strange shapes.The diver himself hears only two sounds: the hiss of the regulator as he inhales and the gurgling of air bubbles as he exhales.These two beats will always accompany his adventure journey.As he descended, the scenery around him changed rapidly, with currents, visibility, ambient light, and marine life all changing with depth.In that sense, even just descending the anchor line can be called an adventure in itself. After the diver dived to a depth of 190 feet, he found a sunken ship. The hull was twisted, cracked, and damaged in a way that Hollywood movies could never show. It showed the extreme distortion of normal objects and natural forces. .Various pipes and wires were exposed from the torn hull.Schools of fish swam in and out of the dilapidated hold.The hull is covered in seafloor vegetation, and only a few of its most characteristic components—thrusts, rudders, portholes—can tell it's a ship.Divers have to envision the rest of the boat in their minds.Only when the visibility of the seabed is good can divers have the opportunity to see the overall appearance of the ship.Otherwise, he can only see the cross-section of the ship.Coupled with the effect of nitrogen narcosis, he may see even less. Divers have about 25 minutes to examine the wreck before returning to the surface.If a clear plan had been made prior to the dive, he would go straight to the part of interest on the wreck and start working.Most divers stay outside the boat at all times, touching the hull, looking for loose parts or taking photos.Their work is smooth and conservative.But the soul of the shipwreck is hidden deep inside the ship, and that is where the story takes place, where the human expression frozen on the face at the last moment can be found.All of the major equipment on board is located within the hull - the telegraph, rudder and compass box that set the ship's course.There were portholes, utensils bearing the seals of sailors and nations lay buried in the ruins, and pocket watches, trunks and champagne bottles were deeply covered in silt.The bronze bell on the ship can only be found inside the hull. Generally, the name of the manufacturer is engraved on the bell, and some clocks also show the time when the disaster occurred. The inside of the sunken ship is an extremely terrifying place, all order is destroyed, and the hull is extremely distorted, and humans cannot adapt at all.The corridor was broken in the middle, and the fallen ceiling blocked the way before the stairs.The nine-foot walkway is only two feet long.The ladies' bridge room and the captain's chart room are also now flipped, tilted, or simply non-existent.The bathtub that had been placed by the wall also disappeared without a trace.Everything shows the tragic scene of the sudden arrival of bad luck.For many, the inside of a wreck is the most dangerous place they've ever been. Divers who want to enter a wreck, especially those who want to explore the depths of a wreck, must have a very different concept of space than they would on land.He had to think in three dimensions to fully understand the concept of the sea of ​​words—turn left, sink, rise diagonally, follow the crack to the right, and so on.He had to have a great memory to remember everything he went through - all the twists, turns, bumps and dips - and he had to do it in an environment with few obvious signs and anemones everywhere at this point.Once his ability to judge the direction is reduced or his memory is blurred, even if only for a short time, it will be a fatal blow to him.He'll start asking himself constantly: Do I swim three or two rooms to get to the captain's cabin?Did I go left-right-left or right-left-right before going up to the turret?Am I changing the horizontal position of the deck unknowingly?Is this the pipe I saw next to the exit, or one of the other six pipes I saw when I swam past here?When these problems arise, the situation can become very bad.This most likely means that the diver has lost his way. It is very dangerous for divers to get lost in a shipwreck.The air in the cylinder is very limited.If he can't find the exit, he will be drowned.Even if he finds an exit, he won't have enough air to complete the decompression if he's running out of air.Nitrogen had already made his head dizzy, and now his brain was entangled with intermittent voices: You are lost, you are lost, you are lost, you are lost, you are lost... He will try to guess a way , but if he did, he would be like a child in a playground, walking blindly would only lead him to dead ends, which would make him even more disoriented.His air is getting less and less, his life time is getting shorter and shorter, just like that, the lost diver ends up perishing at the bottom of the sea. Even if a diver has good bearings, he faces a problem of visibility.200 feet below the sea floor is pitch black, and the interior of the wreck is even darker, sometimes even dark.Headlamps and flashlights worn by divers can provide sufficient light if good visibility is achieved solely by lighting equipment.But wrecks are usually covered in silt and debris.Even the slightest movement of a diver—reaching for a plate, kicking a fin or turning to memorize a sign—could muddy the mud and affect visibility.In this total darkness, the deep sea wreck diver is more like a shadow diver, for whom finding the wreck shadow is finding the wreck. Air bubbles exhaled by divers can also affect visibility.Exhaled air rose, stirring up the muck and rust overhead.Just the breath itself can shake off a rain of rust, some the size of a pea, but most the size of sucrose crystals.The air bubbles also muddy the oil droplets in the water.Oil droplets leaked from tankers and various equipment spread all over the sunken ship. Air bubbles stir the oil droplets into oil mist that adheres to the diver's mask, and may also be sucked into the diver's mouth.At this time, the visibility is even lower, and it is impossible to distinguish front, rear, left, and right.Even the most basic orientation is impossible to discern on a sea floor filled with silt, rust and oil mist. To avoid churning up silt, divers learn to move forward with minimal movement.Some divers move like crabs, using only their fingers to pull their bodies forward.Their fins float motionless in the water.They do not ascend or descend by kicking the water, but by inflating or deflating a float bag, which they use to control buoyancy using the air cells between the tank and the diver.If they find an area of ​​interest, they use their knees and arms to adjust for buoyancy, working on their knees, with only their lower legs rubbing against the wreck's floor. This measure is only a stopgap measure and cannot solve the fundamental problem.Divers exploring wrecks will eventually destroy visibility, it's just a matter of when and how much damage is done.Once the silt billows, rust flakes fall, and oil mist spreads, visibility in the wreck is poor, sometimes for a few minutes, sometimes longer.Even divers with a good sense of direction are unlikely to see the way back.If he kept moving, the silt would churn even more.In zero visibility, it is impossible for a diver to find an exit even if he is only five feet away.Add in the effects of nitrogen narcosis, and even the smallest of problems can become serious, and zero visibility has always been their worst problem.In extreme darkness, the chances of getting lost in pitch-black divers increase dramatically. Problems with orientation and visibility can be enough to affect a diver's mental state.But divers face another, more serious threat.When the ship was severely damaged and sank to the bottom of the sea, all the wires and pipes that were originally laid on the roof, walls and floors were exposed.What was once a luxurious and beautiful place is now full of cables, wires, bent iron rods, bed springs, couch springs, chair legs, tablecloths, pipes and other menacing waste.These things are constantly swinging around the diver, and may catch various bulky parts of the diver's diving equipment at any time.Once hooked, divers are trapped inside the wreck and risk burying themselves in the wreckage if they struggle.These obstacles are difficult to avoid in poor visibility conditions.Any experienced wreck diver has encountered similar situations on the ocean floor, and often. Divers who get lost or trapped in shipwrecks often face death.Bodies found in shipwrecks often have wide-eyed, terrified eyes.Strangely enough, it's often not the dangers themselves that kill the diver, but the diver's response to them—his fear—that makes the difference between his life and his death. Here's what happened to a panicked diver after he became trapped in a wreck: His heartbeat and breathing quickened.At 200 feet below the sea floor, each inhalation takes seven times as much air as on land, and a panicked diver breathing faster and faster can quickly run out of air in his tank.Seeing the pointer of the air capacity meter keep dropping, the diver's heartbeat and breathing will further increase, which greatly reduces his time to solve the problem.Heavy breathing can lead to aggravation of nitrogen narcosis symptoms.The nitrogen narcosis, in turn, will increase the fear produced.This creates a vicious cycle. He reacted quickly and strongly to fear.However, the dangers encountered in the sunken ship are one after another, and the diver's desperation puts him in an even more dangerous situation.For example, a diver who gets lost will panic and run around looking for an exit.His panicked movements will disturb the mud and seriously affect the visibility of the bottom.When he can't see the object, he will look for a way out even more frantically.Going aimlessly would likely get him hooked by overgrown objects in the hull, or possibly cause the collapse of other bulky objects within the ship.At this point his breathing becomes more rapid and he will see his air volume needle drop rapidly again. Divers may yell for help.Sound can travel far under water, but the direction of propagation is scattered, and even if someone hears it, it is impossible to determine the location of the sound.When a diver is trapped alone in a sunken ship, his brain can no longer think of countermeasures, but can only repeat constantly: I am going to die!Be sure to get out!Be sure to get out!At this time, the diver will panic and look for the exit, and the air volume pointer will drop further.The bottom of the sea was pitch black, and by this time it was probably the end of his life. In 1988 a man named Joe.Droz' Connecticut divers set out on the Explorer to explore the Dorian.This is his first time surveying a large underwater shipwreck, a trip he has always dreamed of.In order to ensure the safety of diving, on the basis of the original two cylinders, he added a tank of air-a small emergency backup cylinder. "Just in case," he thought.Droz and two other companions made it through Kimbell Cave.This rectangular opening is Peter, the heir to the Kimbell department store.Kimbell cut open the first class section of the hull in 1981.In the dark green water, the black hole extends down to 90 feet.It's a sight that can terrify even the most experienced diver. Shortly after entering the wreck, a regulator tube on Droz's back became tangled in a 90-foot yellow rope that may have been a marker left by a previous dive.Under normal circumstances, divers will ask their companions to help them untie the rope.But at 200 feet on the bottom of the sea, the divers are under nitrogen narcosis, and everything is in an abnormal state.Droz reached for the diving knife and tried to cut the rope.但他没有按照自己的习惯使用右手，而是使用了左手，可能是因为绳索缠在他的左后方。但这个别扭的动作使他干衣上的排气阀受压，这个结果是他怎么都没有预料到的。在德罗兹切割绳索的过程中，潜水服中的气体开始泄漏，使他的浮力迅速下降。他开始下沉，而深度加重了他的氮醉症状。 德罗兹的身体不断下沉，他已经快到达心理极限了。每次他发力切割绳索的时候，他衣服内的空气就会泄漏一些，他的身体就会进一步下沉。氮醉症状的加剧让他无法想出有效的办法脱离困境。他的呼吸更加急促，氮醉症状越来越严重，形势越来越紧急。德罗兹已经耗尽了第一罐空气，但这时他犯了一个致命的错误，他没有开始使用第二罐常规体积空气，而是用了他的小型应急气瓶。 几分钟后，德罗兹摆脱了绳索的纠缠。这时，他的两个伙伴也已经意识他遇到了麻烦，开始向他游来。但氮醉的症状已经让他失去了理智，空气的泄漏也让他的干衣越裹越紧，他的身体继续下沉，这时他耗完了应急空气，但糟糕的是，他以为用完的是他第二罐常规空气。 他的两个伙伴游到了他的身边。一个抓住德罗兹拉着他向上游出“多利安”号，但由于衣服中空气的泄漏，德罗兹变得越来越重。两名同伴必须采取措施避免德罗兹继续下沉。其中一名潜水员开始给自己的衣服充气，提高自己的浮力以便能够抓住德罗兹升出水面。但现在德罗兹急需空气，而且他认为第二罐空气已经用完，这些念头使他陷入了恐惧的深渊。他猛烈地挣脱同伴，而他的同伴由于浮力过大，急速弹出沉船向水面冲去。由于上升的速度过快，他无法排出衣服内的气体，随着海水深度不断降低，水压不断减小，膨胀的气体使他身体的浮力越来越大。很快，这名潜水员就升到了100英尺的深度，而且还在急速地射向水面。如果他在浮出水面之前没有减压，他不是患上减压病就是命丧大海。在这种急速上升的过程中，他根本无法放出衣服内的空气，而锚绳根本不在视线之内，他只能不住地上升。 而在“多利安”号中，德罗兹吐出了口中的空气调节器，这是极度恐慌之下的生理反应。冰冷苦咸的海水充满了他的肺部。他开始剧烈地呕吐，他眼前已经一片漆黑。剩下的一名同伴试图将自己的备用调节器放入德罗兹的口中，但德罗兹开始用手中的潜水刀疯狂地向同伴刺去。他的思绪开始向四面八方飞散，氮醉不断折磨着他的神经。而后，德罗兹转身向沉船底部游去，背上背着一整罐空气，手中的潜水刀还在不断猛刺，好像要把海水劈成碎片。他一直向下游去直至消失在深渊中，再也没有出来。 他的第二个伙伴也受到了氮醉的侵袭，眼前的恐怖景象可以随时使他陷入致命的恐慌之中。他认为德罗兹和另一名伙伴已经丧生。他检查了一下自己的空气容量，然后发现了他最怕出现的状况：他的时间非常有限，他早该开始减压上升了。他开始上浮，同时认定他是三个人中唯一的幸存者。 事实上，命运为第一个潜水员创造了一个奇迹。在60英尺深处，他成功地放出了衣服内的空气，从而降低了上升的速度。同时他看到了锚绳的位置，对他来说，这简直就是救命绳索。他向锚绳游去，将这根像生命一样宝贵的绳索紧紧攥在手里。他安然无恙地回到了船上。而第二个潜水员完成了减压，也有惊无险地活了下来。只有德罗兹身负一整罐空气葬身大海之中。 并不是所有的潜水员都像德罗兹一样容易向恐慌屈服。优秀的潜水员要学会控制自己的情绪。在迷路或受困的时候，他可以压制住挣扎和逃跑的想法，克服氮醉的影响，排除恐惧的念头，保持冷静，直至呼吸节奏恢复正常，氮醉症状减轻，大脑恢复理智为止。这样他就战胜了人性，具有了超越正常人的能力。这样他就从人类的本能中解脱出来，成为自然界中的强者。 要达到这个境界，潜水员必须清楚地认识死亡，只有这样他才能在直面死亡时应付自如。这个过程通常要历时几年。在这期间他要不断学习、讨论、练习、咨询、规划并要进行艰苦的体验。工作中，当老板公布近期销售数字时，他会一边点头一边想：“不管在海底发生什么状况，只要你活着就是万幸。”付帐单时，或在家看录像时，他会想：“如果在沉船中遇到麻烦，动作一定要慢下来，要对自己说话，让自己冷静下来。”在不断积累经验的过程中，他会参考其他优秀潜水员的建议：“在你考虑下一个问题之前，一定要冷静地把第一个问题解决好。” 普通的潜水员会依靠自己的力量急于摆脱困境，以免其他的潜水员看到自己的窘态。但受过训练的潜水员宁可自己尴尬也愿意保住性命。受过训练的潜水员也不会过于贪心，他知道忙于收集沉船物品时潜水员会放松对方向的记忆，这会威胁生命的安全。即使在氮醉的影响下，他也能清楚地记得，大约四分之三葬身“多利安”号的潜水员身旁都有一大包从船上收集的物品。在收集了六个盘子后又发现第七个时，他清楚地知道，他这时脑海中出现的念头只是氮醉症状导致的幻觉——“如果其他人拿到这个盘子，我就太没面子了”。优秀的潜水员会注意聆听像丹尼。克伦威尔一类的船长发表的意见，他会对围着一桶破盘子和银器的顾客说：“我希望你们好好看看这些东西，摸摸它们。这些垃圾值得你们送命吗？” 潜水员退出沉船后，他就开始了返回潜水船的旅程。如果一切顺利的话，他就会油然而生一种兴奋感和成就感。如果没有成功减压，他就会头晕目眩，一直无法放松。返回水面的过程也充满了危险，足以使最优秀的潜水员致命。 潜水员找到锚绳后开始上升。然而他不能只是像气球一样沿着锚绳上浮。如果在上升过程中放松警惕——比如突然看到鲨鱼或开始走神——他可能就会错过适当的减压点。优秀的潜水员会在上升过程中保持浮力的均衡。在失重状态下，他可以通过轻微的踢水或拉动绳索来推动身体上升，他永远不会放任身体自由漂浮、错过适当的减压点。他会边上升边放出潜水服和浮袋中的空气来保持适当的浮力，避免突然上升。 如果海水很平静，那么潜水员在用于上升和减压的一个多小时中就会非常悠闲。在大约60英尺深的地方，潜水员开始第一次减压。这时很可能已经可以重见阳光。温暖的海水包围着他的身体。海水可能是明亮的，也可能是黑暗的，可能是空旷的，也可能布满了水母或其他小生物。最有可能的是，海水呈现蓝绿色。在这个感受不到重力的世界里，潜水员渐渐从氮醉中恢复过来，不再受到深海中各种危险的困扰，他们开始享受探险旅程中的奇妙景色。 浮出水面后，潜水员游近潜水船，他只需登上船边的金属折叠梯就可以结束他的探险旅程了。在海面平静的时候，一切过程都可以按部就班，但在风浪大的时候，折叠梯就会变成凶猛的野兽，威胁潜水员的安全。 2000年，一个名为乔治。普雷斯的潜水员刚刚完成对一艘近海沉船的探险浮出水面。当他向“鹰巢”号潜水船游去时，海面上风浪大作，雾气遮住了地平线。“鹰巢”号随着海浪上下起伏，这时梯子的横档一下击中了普雷斯的下颚。普雷斯几乎疼得晕过去，他松开了抓住梯子的手。普雷斯被卷入海浪中，漂到了船的后部。潜水包租船的船尾通常都绑有一根“标记绳”——后面系着一个救生圈——以便漂流的潜水员可以抓住，然后将自己拉近潜水船。但是普雷斯无法游到“标记绳”。如果漂流的潜水员超出了“标记绳”的范围，就会有失踪的危险。普雷斯很快就漂过了“标记绳”。 船上有人看到后，赶紧向船长霍华德。克雷恩汇报。但是当克雷恩船长到达船尾时，普雷斯已经失去踪迹。当时由于还有其他的潜水员正沿着锚绳减压，因此船长不能命令“鹰巢”号立即起锚寻找普雷斯。于是船长抓起一部对讲机，冲进了“左迪亚克”号小型追踪船，独自寻找失踪的潜水员。几秒钟后，克雷恩也消失在狂澜之中。不一会儿，他与“鹰巢”号取得了联系，“左迪亚克”号的舷外发动机失灵了。他也开始在海面上漂浮，只有小船被冲到浪尖时才能看到“鹰巢”号的踪迹。这时，普雷斯的妻子——“鹰巢”号上的助手，向外发出了求救信号。但只与一艘渔船取得联系，而且渔船距他们还有一个小时的航程。渔船答应尝试与最近的大船取得联系。至此，所有人都束手无策，只有祈祷普雷斯能够在大西洋的暴风狂澜中生存下来。 三十分钟后，克雷恩终于修好了“左迪亚克”号的发动机。但他此时已经漂得太远，根本无法找到普雷斯的踪迹。他回到了“鹰巢”号上。不久，“鹰巢”号收到一个信号。附近的一艘渔船发现了普雷斯——距离“鹰巢”号5英里，仍然活着。他已经在海上漂了两个多小时。在所有潜水员都安全返回船上之后，克雷恩终于找回了普雷斯。“鹰巢”号上的所有潜水员都认为这简直是奇迹。 只差十秒，普雷斯就会圆满完成历时90分钟的潜水，但他在这短短的时间里与死神擦肩而过。这次事件再次说明了沉船潜水运动的危险性，以及从事这项运动所需要的坚强意志和生命力。 在沉船潜水运动中，只有最终返回潜水船，才意味着得到了真正的安全。