Into the Deep

Bret GilliamJust as a drive through some inner city areas might prompt a bit of defensive driving and safety precautions, your jump off the back of the boat into the deep should inspire some defensive “diving” and a solid understanding of the most identifiable potential hazards. Let’s take a short look at the usual suspects you can expect to find lurking somewhere in the abyss.

Nitrogen narcosis: Most divers have experienced this phenomenon to some degree. The effects of nitrogen at elevated partial pressures much above 4.0 ATA, the equivalent of 130 fsw, can produce varying symptoms from mild “fuzziness” to near incapacitation and collapse. Forget about nonsense like “Martini’s Law”; narcosis is entirely subjective and will induce different reactions in each individual. Compressed air is a viable breathing media for most experienced divers, if trained properly, down to around 200 fsw. But it is vital that initial forays beyond traditional sport depths be under the supervision of a professional technical instructor who is capable of recognizing your impairment and helping you understand those limitations.

Continued exposure to a regular regime of deep diving has a certain adaptive effect whereby narcosis is lessened in many individuals. However, a small segment of the diving population will hit a finite physiological wall at some depth and they should never venture deeper. Elevated partial pressures of carbon dioxide (CO2) will increase the onset and severity of impairment. Narcosis is a factor on every deep dive. Develop a thorough understanding of this effect and plan accordingly.

Oxygen toxicity: Probably more misconceptions have been centered around central nervous system (CNS) toxicity (known as the “Paul Bert effect”) than any other diving hazard. Realistically the threat of a CNS hit is very low on compressed air dives above 200 fsw. This depth produces approximately 1.5 ATA of O2 with an allowable exposure of two hours on a single dive. This is, of course, less than the recommended maximum of 1.6 ATA of O2 for working divers and provides a huge cushion of time since it would be difficult for a diver to physically carry enough breathing supply in open circuit scuba to reach the two hour limit.

Most errors in dive planning occur when the diver fails to account for the total “dose” of oxygen. This means counting the bottom depth exposure and the decompression time for a total. A diver breathing pure oxygen at 20 feet during his decompression is at 1.6 ATA of O2. In some dive profiles a higher oxygen dose is received during decompression than during the bottom depth phase of the dive. Like narcosis, elevated CO2 is a triggering mechanism. Other common mistakes include rigorous tracking of “whole body” or pulmonary oxygen toxicity (known as the “Lorraine Smith effect”). This is unnecessary since dives planned within CNS limits will never approach a threshold of vulnerability for pulmonary problems.

All deep divers should familiarize themselves with allowable exposure times and never run times to the limit. Risks from exceeding limits or for idiosyncratic reactions to lower exposures include convulsions that could drown the diver. Be sure to balance both the working dive at depth with the decompression if oxygen or nitrox is used.

Decompression sickness: Arguably there is no hard data to suggest that deeper diving presents any higher statistical incidence of DCS than longer, shallow dives. In fact, most DCS hits occur between 60-90 foot depth exposures. However, deeper diving usually involves planned decompression and most divers have not been adequately trained in technique and procedures in mainstream sport classes. The added discipline of ascent rates and maintaining precise depths during stops is an acquired skill for most people. And with the addition of strong currents and the burden of handling heavier equipment rigs, it is advisable to seek every hedge against risk.

Plan for extra reserves in decompression gas supplies and employ pure oxygen or 80/20 nitrox for its increased efficiency in outgassing absorbed nitrogen. Adopt diving habits that limit hard work and swimming. And learn to recognize DCS signs and symptoms in both yourself and your dive team. Carry emergency oxygen deliverable by demand mask or regulator on the boat and don’t hesitate to use it.

There’s no big mystery about DCS and sooner or later you or someone you dive with may experience “the bends”. You can do everything within decompression model limits and even with an extra dose of conservatism still fall victim. That’s the breaks, there’s no shame in it. What’s bloody stupid is not reporting symptoms or seeking treatment. If you approach deeper diving with the proper respect and due diligence for the decompression, you are probably at no more risk than any diver.

Stress: The unexpected circumstance in an unfamiliar environment can rattle anybody. Add a component of depth where narcosis or breathing resistance can be a factor and stress levels can skyrocket. In deeper diving, we are usually task-loaded to a higher degree than the guy doodling around on a shallow reef. Keeping track of time, depth and remaining air supply while managing a set of doubles and an extra deco cylinder doesn’t allow a whole lot of attention to be paid to other outside stimuli like the ball of monofiliment line that snags you or an unstoppable second stage free-flow at 175 feet.

Keep cool, stay in control and follow contingency protocols taught in training. Most accidents in deep diving can ultimately be traced back to panic induced by stress. If you have known heebie-jeebies such as claustrophobia, don’t decide to take up penetration wreck diving at 160 feet. Better than anyone, you can assess potential problem areas in your individual psyche. Then have the common sense to avoid those situations.

Another common stress disorder is invoked by simply overloading yourself with more gear than you can comfortably handle and swim with. I’ve seen divers ready to collapse from the weight of their equipment package before they’ve even gotten in the water. Common sense goes a long way. And it’s cheap. Use plenty of it.

Marine life and Mother Nature: In other situations if you encounter some nasty creature you can simply decide to make a dignified exit. But if you’re staring down the face of an aggressive shark with another 45 minutes of decompression obligation… well, your options get a bit more limited. That’s what buddies are for: so sharks can eat them first.

Seriously, almost any marine life threat can be dealt with by a dive team if they keep cool. Sharks are notoriously over-rated in their actual menace to divers and even the most curious can be discouraged with a solid reaction such as poke in the nose. More insidious are dangers from stinging organisms such as sea wasps or Portuguese Man-of-War. These are most likely to be found in the shallow decompression depths where many divers tend to be inattentive during long boring hangs. Pay attention, have at least one team member actively watching the area to alert the team to hazards.

And never forget that Mother Nature has a bit of whimsy that seems to delight in throwing in unexpected currents that blow divers off wrecks and cause them to miss their anchor lines. Or the violent thunderstorm that appears from a clear summer sky while you’re on the bottom and your support boat drifts away. Be prepared for contingencies with lift bags to do drifting decompression under, deployable safety sausages on lines that you can run up to the surface while drifting underneath, flares or flashers for night signaling, and self-contained decompression gases. And always have a low pressure sonic Dive-Alert ready to blast when you surface.

He who prepares and anticipates his adversary, whether narcosis or the great white shark, will handle the situation well. And likewise, he who hesitates… is lunch!

Bret Gilliam
54 Stonetree Rd.
Arrowsic, ME 04530

Rating: 5.0/5. From 1 vote.
Please wait...

4 thoughts on “Into the Deep”

  1. Great site – always good info with a few chuckles thrown in. Your first edition of ‘Deep Diving’ was absconded from me by another diver in the coastal jungles of Costa Rica many years ago by a friend I got to know down there back in the mid 90’s. He was living down there and since I was on my 2nd reading figgured he could use it more than myself. We had discovered a deep hole in the sandy bottom at 150′ on a dive and we just peered over the ledge into the darkness thinking, ‘gotta do that’. Returned the next day and proceeded with a line from the boat, and just as we reached the hole at 150′ three bull sharks honed in on us out of that deep caribbean blue like torpedos shot out from a sub out there somewhere. I’ll never forget that sight! They circled us perhaps thinking of fresh tuna and needless to say we had to beat a hasty retreat following our line back up, actually fin kicking them off getting back into the boat. We talked about trying it again but somehow never got back to it. Several months later back in the states your second edition of that book was out and I picked it up. It is a book full of info and I suggest most divers should have a copy if they do anything other than cattle boat resort diving — Actually over the years I was always glad I had that book to leave off with that guy as he also was into exploratory diving and just maybe some of that knowledge kept him out of trouble. Keep on trukin’ dude— Tom Drewien

    No votes yet.
    Please wait...
  2. What a great read, and hearty chuckle at the “deco stop with buddies, so the shark can eat them first”. Reminds me of the “you don’t have to out run a bear, you only have to out run your buddies”

    No votes yet.
    Please wait...
  3. John,

    You’re not the only one this situation has happened to and your instincts were correct. In many cases, an experienced diver with a background in even basic navigation and orientation will have more technical grasp of what to do in unanticipated circumstances than a Third World launch driver. If you find yourself in doubt as to his actions, question him about his experience and thought process of determining his location and direction to proceed. Then survey the other occupants of the launch to see what their own backgrounds might be with maritime experience. It may well be that your group has more individual or collective experience and competence that can be brought to bear. Of course, the best situation would be to have a credentialed merchant marine captain within your diving group since most of these types can “navigate” with minimal references or equipment. In such cases, a diplomatic “takeover” would probably be the best solution.

    As you know, I’m a Merchant Marine licensed Master and I wouldn’t hesitate to put my input forward early and aggressively if I thought the local driver was having problems. I always make a point of familiarizing myself with local charts, current patterns, tides, prevailing landmarks, etc. when in isolated areas. And I’ve never encountered a “lost” situation that could not be sorted out. I also take detailed inventory of safety equipment and communications capabilities on dive launches. I like to see a one-day fresh water supply stored on board somewhere as well. Don’t ever doubt the fact that “shit happens”.

    It does remind me of the time that American frontier explorer Daniel Boone was asked if he had ever been lost before during his explorations as he pushed west into the unknown interior of the early U.S. He replied, “I’ve never been lost before… but I was damned confused for a couple weeks several times.”

    He found his way eventually and you probably will, too!

    No votes yet.
    Please wait...
  4. What would you do about this one, Bret??
    We had an interesting trip back from Sorido Bay (West Papua) recently in a small boat to join Mandarin Siren, a liveaboard, in Sorong. The heavy rain produced a white-out.
    It was after about an hour and a half that our boat driver asked if we had a compass. I remembered Sorong being at about 120 degrees from Kri with islands to the right. Out driver insisted on steering North East. After about another hour we were still in white-out conditions with no sign of land and my temper was getting frayed. I was sure we were going the wrong way. At what point does one mutiny and take over the controls?
    Eventually we got a signal on the iPhone and the GPS showed us to be well north of the Bird’s Head Peninsular, on the way to mid Pacific. At this point we needed to steer South West! I took the controls.
    Our driver was not convinced. Eventually we met a fishing boat and he asked directions! We followed the fishing boat south-west until we sighted land. We got to Sorong on the second reserve tank of fuel. The crew of Mandarin Siren had been getting worried about us. Me? Worried?

    No votes yet.
    Please wait...

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.