In outer space, you pass out in about 15 seconds from lack of O2 to the brain, then your heart stops and eventually you freeze. NASA has done the experiments:

In outer space, you pass out in about 15 seconds from lack of O2 to the brain, then your heart stops and eventually you freeze. NASA has done the experiments: > Chimpanzees can withstand even longer exposures. In a pair of papers from NASA in 1965 and 1967, researchers found that chimpanzees could survive up to 3.5 minutes in near-vacuum conditions with no apparent cognitive defects, as measured by complex tasks months later. One chimp that was exposed for three minutes, however, showed lasting behavioral changes. Another died shortly after exposure, likely due to cardiac arrest. Then there was this oops: > In 1965 a technician inside a vacuum chamber at Johnson Space Center in Houston accidentally depressurized his space suit by disrupting a hose. After 12 to 15 seconds he lost consciousness. He regained it at 27 seconds, after his suit was repressurized to about half that of sea level. The man reported that his last memory before blacking out was of the moisture on his tongue beginning to boil as well as a loss of taste sensation that lingered for four days following the accident, but he was otherwise unharmed. https://www.scientificamerican.com/article/survival-in-space-unprotected-possible/ https://www.scientificamerican.com/article/survival-in-space... Dying in a submarine would be very different. The pressure differential in space is a single atmosphere. Water increases by about one atmosphere every 33 feet. At Titanic's depth it's ~ 368 atmospheres of pressure. Reddit discussion from 3 years ago: https://old.reddit.com/r/submarines/comments/gy1wc6/what_exactly_does_happen_when_a_submarine_goes/ https://old.reddit.com/r/submarines/comments/gy1wc6/what_exa... > The collapse of a submarine pressure hull happens quick, just 37 milliseconds in the case of the Scorpion. The incoming water had a velocity of about 2,000 mph. [...] Over such small time scales, there is no time for the water or the steel hull to absorb any heat from the rapidly compressing air inside of the submarine. Because no heat is transferred from the air to the water or hull, the compression is adiabatic. [...] The collapse halted when the air pressure was approximately equal to the water pressure at 1,530 feet, which is 4,630,000 Pa. [...] 1,122°F. That was at 1,530 feet. Contact was lost with the Titan at 1 hour and 45 minutes into its dive. A typical dive to the bottom took it 3 hours. So it was likely at least halfway to the bottom (6000 feet). Its implosion would have involved even more spectacular forces. They were dead before they knew what happened, incinerated and pulverized. There are no bodies to recover. https://en.wikipedia.org/wiki/2023_Titan_submersible_incident https://en.wikipedia.org/wiki/2023_Titan_submersible_inciden... See "Why the USS SCORPION (SSN 589) Was Lost 50 years Ago" https://www.iusscaa.org/articles/brucerule/scorpion_loss_50years.pdf https://www.iusscaa.org/articles/brucerule/scorpion_loss_50y...