What is the maximum depth a human can dive to?

Answer

Essentially there is no limit.¹ If the question is restated as "how deep is possible on compressed air" Some of the answers below are accurate.

The options for modern exploration are most commonly open circuit scuba and rebreather. Diving is limited by the correct mixture of breathable gasses. On open circuit "classic" scuba the gas must be mixed ahead of time, while on rebreathers a diver always has the right mix of gas for the depth. Mr. Dave Shaw Demonstrated on a modified recreational rebreather successful diving to 888ft of fresh water.²

1.) See Dave Shaw and rebreather diving

2.)http://en.wikipedia.org/wiki/David_Shaw_(diver)

Answer

The maximum depth that you can dive safely on air is dependant upon the partial pressure of oxygen. The air that we breathe at the surface is at a partial pressure of 0.2 bar .The partial pressure increases as your depth increases for instance at 10 metres it will be 0.4 bar and at 20 metres it will be at 0.6 bar etc. The oxygen becomes toxic at approximately 1.6 bar partial pressure effectively giving you a maximum safe diving depth on air of around 70 metres. I would not recommend diving up to this depth on air as you will be diving to the extreme edge of air diving and as with all individuals tolerances may vary.

Mal

Answer

The maximum depth someone can dive will be directly related to the percent of oxygen in the breathing mixture. The air mixture we as humans breath is mostly made up of oxygen and nitrogen. The ratio is around 80% nitrogen and 19% oxygen and 1% other gasses. The same gas, oxygen, that keeps us alive can become toxic and kill us under high pressure. I can't remember the depth but I think it was around 335 ft. sea water that oxygen becomes toxic. How do we prevent oxygen toxicicity? Reduce the concentration of oxygen and replace it with a different gas. Say helium for instance. Since our bodies only use about 5% of the 19% of oxygen we breath, we can replace a portion of the gas with something that is relatively safe under pressure. This is called a tri-mix gas. I don't know what the limits are for tri-mix diving. A couple of other things that divers who dive over the recreational limits of 60 ft. deep are nitrogen narcosis and HPNS (High pressure nervous syndrome) Narcosis is what a diver can feel when nitrogen is under pressure. Many divers say it is similar to being drunk or a narcotic effect thus the name. HPNS can cause anxiety, uncontrolled trembling, nasuea.

To answer your question, check the Guiness Book of World Records to find the deepest dives made with SCUBA equiptment, tri-mix, and holding your breath.

Safety & blue skies...

Answer

Mark Ellyatt (UK) currently holds the (unconfirmed) world record for the deepest dive using SCUBA. The dive of 313m beat the previous record set by the late John Bennet of 308m (confirmed).

The above records were set using 'recreational' SCUBA. Commercial dives to depths greather than 500m have been made using specialised commercial and military diving equipment and support systems.

Answer

I recall one free dive with no air supply to over 1,000ft. I also recall a few fatalties attempting this.

On Sport SCUBA, 100-130ft is the informal but accepted max depth most certification agencies recommend.

A different Interpretation.

As the previous answers all indicate in one way or another, the primary limiting factor in most cases at least is PPO₂ and various gas results (including hypothermia, which gases like helium exacerbate). However, in super-high pressures, there is a problem with denaturing of various proteins in the human system. This rare and unlikely problem is still in the books and not reality, as dropping a human to that depth and ambient pressure has, to the best of my knowledge, never been tried. While we dropped the Glomar Challenger to approx. 36,000ft in the 1960's (Mariannas Trench), the people inside were protected at one atmostphere. It's likely that, when exposed to pressures of a couple hundred atmostpheres or more, human physiology just won't keep up, for reasons unrelated to gas problems.

First answer by Donald. Last edit by Cjonb. Contributor trust: 102 [recommend contributor]. Question popularity: 180 [recommend question]