When subs or ships sink, at what depth does the human body implode or blow up?
When a submarine hull fails at its crush depth, the first crack propagates at the speed of sound in steel (or whatever the hull is made from; titanium is also used). The crack reaches its maximum width in a tiny fraction of a second.
The surrounding water, under hundreds of tonnes per square metre pressure, rushes in immediately at speeds of hundreds of metres a second, compressing the air in the submarine. The rising pressure heats the air ahead of the water, so that it can reach the ignition temperature of many burnable substances.
The wreck of the USS Scorpion
In the case of the USS Scorpion, which sank in 1968, the hull failed at 470m depth (a pressure of ~47 atmospheres). By the time the compressed air in the hull reached equilibrium pressure with the inrushing water, it had been raised to a temperature of roughly 600°C (1100°F). Paper will burn at around 230°C (~450°F), for example.
However, any burning that occurred would have been quenched by the inrushing water in less than a tenth of a second, so whether this would have counted as an explosion, I’ll leave to others to argue about.
Being hit by a mass of water moving at 900 metres a second (2,000 mph) will count as “crushing” by most people’s definitions, I think. Merely falling into water at a human being’s terminal velocity in air (about 130 mph) will break most bones in a human, and rip internal organs from their accustomed positions, so a wall of water moving at 2,000 mph should do at least as much damage.
Mercifully, the crew die faster than their nervous systems function.
So, the short version is that the human body may both explode and be crushed at the crush depth of their submarine; consult your operator’s manual for details.
Sharing stuff like this will make you popular with some people at parties and annoy others. Kind of like sports and politics. Heavy drinkers and chemical abusers won’t care one way or the other.