How to die at sea?

BlueBottleBlueBottle Australia Join Date: 2018-02-03 Member: 236674Members Posts: 306 Advanced user
(Ok this is aimed at just diving geeks, or those with a ghoulish disposition. It's not meant to comment on realism in video games or anything. Peace).

You can scuba dive below your submersible's crush depth because you are breathing air regulated at a pressure equal with the ambient surrounding water pressure. There's no pressure differential to injure you!

Makes sense right? But being crushed like a bug is only the start of your worries.

Inert Gas Narcosis
'Raptures of the Deep' or simply the 'narcs' are similar to drunkenness: Quite fun and stupid. At 30m you can get a bit tiddly. Below 40m there is a risk of experimenting with water breathing or just simply blacking out and letting your regulator fall out that way. These depths can vary a lot, depending on your fitness, training and possible use of exotic breathing mixtures. Best success to reduce its onset are mixes using helium (in place of the normal 78% nitrogen). But your chances of the narcs will still always increase with your depth.

Running out of Air
That's simple stupidity right? It's actually really easy to do. Breathing air regulated at ambient pressure means you use it up really fast. How fast? Each 10m adds one atmosphere (1 atm) worth of pressure. So at 10m you're sucking down your regulated air at x2 normal rate. At 30 meters at x3. ... At 500m (the open diving record) you're breathing at x50, so a regular tank that lasts you an hour at the surface air is now worth little more than a minute. This situation is compounded by the fact that even very short dives below 100m will require you to spend time doing decompression stops on the way back to the surface.

Decompression Sickness
The Bends. Often elected as the better option by divers in the above dilemma. The backstory here is when you open a bottle of coke all the gas fizzes out. This is because it was bottled with gas under pressure. When opened, it's back at one atmosphere pressure which is too low to keep all its gas in a dissolved state. Same thing happens when you breathed your air at pressured at several atmospheres and then swum up too fast. As your blood begins to fizz the effects depend on where these bubbles are and how big they are. On a good day you might get by with crippling joint pain. On a bad day a bubble can rip through you spinal cord tissue. Nice.

Oxygen Toxicity
Oxygen is very good, but it's also very corrosive. Our bodies are designed to cope with this corrosion at normal 1 atm concentrations (only 21% of air). Breathing it concentrated at higher pressures seems to start a runaway corrosion of cell membranes. Cells of those organs you'd otherwise like to function normally. Troubling side effects include lung damage, retinal detachment, and seizures.

Weakness, disorientation and eventually unconsciousness, death. Sure, it's cold down there deep, but there's some additional risks. When you can't keep pace with your body's energy demands then your temperature regulation will eventually go legs up. Just breathing can do this. Breathing 1atm pressure air a costs only a little energy - achievable even by a couch potato. Breathing at 50 atm air is x50 thicker so you're burning a lot more calories. As Helium is often used to replace nitrogen to deep diving mixes you'd think this much thinner gas would reduce the problem. Unfortunately its a cruel twist of physics that helium dissolved in the blood makes heat loss to the surrounding water even faster. Heated suits are a real bonus.

High-Pressure Nervous Syndrome
Another side effect of breathing helium under pressure. This gets serious below 300m. By choosing a helium mix you've replaced your amusing Raptures of the Deep with whole bunch of Parkinson's like symptoms: Tremors, muscular jerking, visual disturbance, nausea, dizziness, and ironically, decreased mental performance.

So just how deep should I safely scuba dive?
Currently, the open-sea diving depth record (outside a Prawn-type suit) of 534m was achieved in 1988 by a team of pipeline connection divers training in the Med. But this may be impractical for you without dozens of support staff, tons of equipment and days for decompression in hyperbaric chambers. So as a sports diver you might want to stay above 300m. After all only 35 people have ever achieved this, and there is nothing to say you will necessarily join the many who have died in various record setting attempts.

Safe swimming!


  • baronvonsatanbaronvonsatan TX, USA Join Date: 2016-12-01 Member: 224415Members Posts: 447 Advanced user
    I knew almost none of this. Thanks for sharing! For my part I'm just gonna choose to believe the basic Alterra environmental suit handles or at least mitigates all that. :p
    This is dumb, but a click a day helps me out a little.
  • BlueBottleBlueBottle Australia Join Date: 2018-02-03 Member: 236674Members Posts: 306 Advanced user
    edited November 9
    Yes, but one can never be too careful. Does Alterra retail a water-heated potato suit (XXL)?
    (asking for a friend)
Sign In or Register to comment.