From the Depths: Life Lessons from a Scuba Divers Perspective
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Introduction To Scuba Diving
For all its importance, he explains, the invisibility of the underground world leaves it off the conservation priority list. So the expedition also made it a goal to publicize the importance of blue holes and the threats they face.
We instinctively associate life with oxygen, but living things existed on Earth for more than a billion years in the absence of the one gas divers can't last minutes without. Jenn Macalady, an astrobiologist at Pennsylvania State University's Department of Geosciences, is studying the water chemistry of Bahamian blue holes to understand the conditions most similar to the earliest, oxygen-free environments that supported life.
She's especially interested in the period from about four billion years ago—when life first appeared on Earth—to what scientists call the oxygen revolution, some 2. By investigating bacteria that thrive in the anoxic waters of blue holes, she can postulate what may exist in the oxygen-free, liquid-water environments of distant planets and moons.
Veteran cave diver Brian Kakuk lifts a more than 3,year-old Cuban crocodile skull—an animal no longer found in the Bahamas—from sediment in Sawmill Sink. Nearly oxygen free, blue holes preserve bones intact. Macalady doesn't dive, but she's an active dry caver who hauls tanks, coils ropes, and chats with young Bahamians about cave slime and the possibility of life in the universe. At her direction, divers take water, bacteria, and hydrogen sulfide samples at depths ranging from the surface to feet. Most of her studies—including DNA testing, bacterial culturing, and the search for molecular fossils—must wait until she gets back to the equipment in her lab.
But hydrogen sulfide is too unstable to transport, so she analyzes water samples for gas levels with a portable spectrophotometer at the dive site. By comparing sulfide densities with water depth, she's learning where different species of bacteria are likely to concentrate in a given blue hole and which mechanisms they use to survive. She is aided by Nikita Shiel-Rolle, a Bahamian cave diver and marine science graduate student at the University of Miami.
Stargate's entrance lies on land that's been in her family for generations. As Kakuk and I emerge from the hydrogen sulfide into the black water below, my nausea and headache quickly pass. I'm relieved not to have to put into practice the suggested method for vomiting underwater, to say nothing of the impact my breakfast—a biological mushroom cloud—would have on the fragile environment.
We descend slowly along the cave's east wall until a triangular portal appears in our lights: the entrance to a 2,foot-long tunnel known as South Passage. Stargate consists of a central shaft some feet deep, with passages extending north and south. Kakuk has explored North Passage about 1, feet out from the central shaft, edging ever closer to the next blue hole to the north, and he's pushed even farther into South Passage. Of the more than one thousand blue holes believed to be in the Bahamas, less than 20 percent have been probed, and Kakuk estimates that three-quarters of those offer passages never seen before.
The great age of Bahamian blue hole exploration lies ahead. The entry to South Passage is decorated by spectacular calcite formations, or speleothems, from drapery thin, curtain-like formations and straws fine, cylindrical deposits like soda straws to the more familiar stalactites and stalagmites. Remember, stalactites need to cling tightly to the ceiling above.
They built up during ice ages, when the sea level dropped dramatically, leaving the caves dry. For Peter Swart, professor of marine geology and geophysics at the University of Miami, speleothems hold a priceless record of climate change in every year of their growth—at the inexorable rate of one to five centimeters every thousand years. By studying speleothems in detail, Swart, Broad, and Amy Clement, a climate modeler at the University of Miami, will gain valuable information about sudden climate shifts of the past.
These include prolonged storms that blew Saharan dust across the Atlantic from Africa thousands of years ago, leaving high concentrations of iron in the stalagmites and red stripes visible in the sediment of cave walls. Information from speleothems will shed light on today's rapid warming and the associated rise of sea level. At Kakuk's direction, I tie off our safety reel to the line at the entrance of South Passage and follow him inside. In the play of our lights, the natural geometry of the corridor is breathtaking.
Above soars a vaulted, triangular ceiling; below, a floor of impenetrable darkness. There is an eerie quality of intention—the vaulted corridor seems more designed than randomly occurring—and I'm reminded simultaneously of the outer walls of Mycenae and the gallery in Khufu's Great Pyramid.
Covering my light with my palm, I hover and watch Kakuk's single lamp move steadily forward as the walls' steep angles come into view. I had expected a measure of anxiety in such an alien environment, but for all its unearthly surrealism, this motionless, lightless place is profoundly calming. For a moment I relax completely, releasing an attenuated breath and swinging my light upward through the swarm of ascending bubbles. Two hundred lateral feet into South Passage, Kakuk collects a water sample for Macalady in a plastic tube.
He points out a fish with a shimmering, translucent tail that flickers like a candle flame—a Lucifuga, about five inches long. Like most life-forms in these lightless depths, the fish is blind.
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Then Kakuk directs my attention to a Barbouria shrimp, a reddish, two-inch crustacean with long, bowed antennae for sensing prey in the darkness. Minutes later, he pauses and shines his headlamp on his fingertip—his signal for the presence of the tiniest creatures. It's an ostracod, a crustacean no bigger than a sesame seed, its brilliant pink interior sheathed in a transparent, clamlike shell. High on its round body, a pair of antennae flutter like fairy wings, propelling the animal through the water.
Kakuk is known for his ability to spot things most other divers—including trained scientists—never see. In recent decades Iliffe and other scientists have discovered an astonishing abundance of previously unknown organisms in these and other flooded caves around the world: more than new species, 75 new genera, nine new families, three new orders, and a new class, Remipedia, first documented in in the Bahamas.
Most cave-adapted species are crustaceans, and many, like the remipedes, are "living fossils"—live species closely resembling those preserved in the fossil record. Iliffe says that the greatest percentage of saltwater cave species come from blue holes in the Bahamas, including 18 of the 24 known species of remipedes. Remipedes emerged million years ago and give scientists a rare look at life in the Carboniferous period—tens of millions of years before dinosaurs appeared.
With slender, segmented bodies less than two inches long and usually colorless and blind, remipedes are, nonetheless, at the top of the food chain in their habitats, using hollow, venom-injecting fangs to kill shrimp and other crustaceans. As we fin deeper into South Passage, the only sound is the rhythmic hiss of our regulators and the rumble of our exhaled breaths.
Kakuk occasionally traces a broad circle with his light on the passage wall, signaling the question, "OK? I've known Kakuk less than two months, but my life depends on his judgment, and his, to some degree, on mine. Nearly seven miles of the cave have been explored since the mids.
In cave diving, redundancy is critical. If one of my lights goes out, I have three in reserve. Our gas supplies—in this case oxygen-enriched nitrox, a combination of oxygen and nitrogen—are backed up with two independent tanks and regulator systems. As long as we follow the rule of thirds one-third of your total gas going in, one-third coming out, and one-third in reserve for emergencies , we should always have enough to get home—even if one of our tanks or regulators fails. That's assuming we don't lose our guideline. In the labyrinth of passages, separation from the line can be fatal.
In my training, Kakuk had spun me around with my eyes closed and towed me away from the line to simulate disorientation. Groping blindly and using my safety reel to search in a spoke pattern, it took me 12 interminable minutes to find the line. One of Kakuk's students was so traumatized by this drill that he bloodied his hands clawing for the line along a cavern roof. For his part, Kakuk has logged some 3, cave dives without serious injury. Given the risks, the lighthearted mood of Broad's team belied this fact: Combined, these divers have participated in dozens of body recoveries from submerged caves.
Some feet into South Passage, we reach the end of the main line, tied off to a bollard of calcite at a depth of feet. Here the tunnel narrows and plunges to below feet. On previous dives, Kakuk had extended the line 2, feet farther, but at my level of experience, we've come as far as he'll allow. We check our air—the first of our thirds is nearly depleted—and turn for home. At the portal separating South Passage from Stargate's central shaft, Kakuk covers his lights and stops. The faint green of daylight in the shaft beyond is just strong enough to cast the walls of the passage entry into silhouette.
I allow my limbs to hang freely, my body rising and sinking almost imperceptibly with each breath. Time appears to stop. I'd like to float here for hours, weightless and relaxed, suspended in the void, all thoughts draining from my mind. Ascending slowly to a depth of 60 feet, we pause at a sloping ledge directly below the cave mouth. In the middle of the ledge is a long trough packed with silt. Kakuk spotted this promising feature on an earlier dive and now reaches into the mud.
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He gropes gently back and forth and—so quickly it seems miraculous—extracts a long bone the color of mahogany: a human femur. This is due to carelessness on behalf of the diver and in most cases can be avoided. Scuba diving does carry risk and it is classed as a dangerous sport. But the risks can be mitigated by diving using safe diving practices.
History of Scuba Diving
The biggest dangers divers face is themselves. For example, please read the section where I answer the question about 'is scuba diving dangerous at 30 feet? The chances of dying whilst scuba diving are very low. Plus quite avoidable. When I researched whether scuba diving is more dangerous than skydiving , it turns out that it is. For scuba diving 1 in 34, die each year, which is roughly three times more dangerous than skydiving. But as already mentioned, the risks associated with scuba can be mostly avoided.
Please see below for more details of how to minimise the various risks associated with scuba diving. The number one reason it is classed as an extreme sport is because the environment you are entering is totally foreign.
That is; you can only dive with the aid of breathing apparatus. Scuba diving becomes an extreme sport simply because if your life support system I. I know that sounds a bit grim, but unless you truely understand the dangers associated with scuba diving, you may not totally respect the rules. The other reason why scuba diving is thought of as an extreme sport is due to the view of Insurance companies.
Many travel insurance companies either exclude scuba diving or limit the depth at which the cover will count for insurance purposes.
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The number one reason why scuba divers die is due to running out of air. In my opinion there's no excuse for this, but it happens too often.
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It's quite simple, when you're scuba diving you are in a foreign environment and if your air runs out, you are in trouble. The best way to avoid running out of air is to regularly check your air contents gauge. When I say regularly, I mean about every fifteen minutes or so. You may feel this is excessive, but by checking your air on a regular basis will get you into a good habit and it will mean you never run out. Also, always leave the bottom of your dive with enough air to get you to the surface with at least 50 bar psi in your air tank.
This includes haivng enough air for a safety stop at metres feet for three minutes. Also, by making sure you always dive with a dive buddy, should you run out of air you will be able to call upon your dive buddy's alternative air supply to get you to the surface. A middle ear barotrauma is caused by the damage done by increased underwater pressure on the air pocket in the middle ear. The damage is a perforated eardrum which results in vertigo and pain. Avoiding a middle ear barotrauma is very easy. Firstly, avoid scuba diving with a cold or congestion.
Secondly, always make sure you clear your ears regularly on your descent of your scuba dive. I always recommend you begin to clear your ears as soon as you leave the surface. Diver decompression sickness is much more serious than an ear barotrauma. Having decompression sickness at its worst can result in scuba diver death. The safest way to scuba dive and avoid decompression sickness DCS is to always dive no decompression stop dives. However, having said that you still need to follow the correct ascent speed. The speed at which you must ascend from your dive should be no faster than 30 feet per minute.
Or put another way; ascend slower that your smallest exhaust bubbles. For example, some scuba divers become euphoric as a result of nitrogen narcosis. This euphoria can lead to the diver removing their mouthpiece or demand valve. The other manifestation resulting from nitrogen narcosis is extreme fear and dread.
This could result in panic and lead to other associated problems underwater. Nitrogen narcosis mostly kicks in at deeper depth dives. This is mostly on scuba dives in excess of 30 metres feet. The real way to avoid the chance of getting nitrogen narcosis would be to stay shallower than 30 metres.
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But in doing so, make sure you build up your depth slowly. Build up slowly to this depth of dive. Also build up your resistance to the the amount of nitrogen in your system that could lead to narcosis, as this seems to reduce the chances of it occurring. Also, as with every dive and in line with safe diving practices, always dive with a buddy.
That way should something happen to either one of you, the other buddy will be there to help. Prolonged breathing of atmospheric air at this depth will lead to oxygen toxicity and can in the worst case scenario cause death. The simplest way in which to avoid oxygen toxicity is to avoid going too deep on atmospheric air. But if you are going to dive deeper than 50 metres feet , then take a scuba diving course on diving at depth. This will teach you the way to dive with other gas mixes to reduce the percentage of oxygen in the air you breath.
An arterial gas embolism as a result of a lung over expansion is extremely dangerous. In the worst case scenario an arterial gas embolism can lead to death. A lung over expansion can be caused by holding your breath on your ascent. As you ascend from a dive the pressure around you reduces. If you continue to hold your breath, ultimately your lungs would rupture. This is what would lead to an arterial gas embolism.
The way to avoid an arterial gas embolism is to follow one of the golden rules of scuba diving, which is to never hold your breath. Always, always breath normally when you are scuba diving. That way you will be safe and therefore avoid lung over expansion. One of the dangers of diving is having equipment failure. Probably the worst failure you could suffer is an aqualung failure. Your life support system consists of your demand valve and your air tank. Equipment can and does go wrong. The first way to avoid problems with your scuba diving equipment is to have it serviced regularly.
The second way to avoid any associated consequences of equipment failure is to follow the second golden rule of scuba diving, which is to never scuba dive alone and to always dive with a dive buddy. If your breathing apparatus fails, which it can do, you need your buddy there with their spare air or octopus system for you to breath from. This will enable you both to return to the surface safely. As already noted above, I am living proof that things can go wrong with an aqualung. There are many types of scuba diving. Some of the types of diving are more dangerous than others.