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This popular YouTube video which is about surviving when jumping from a plane with the parachute failing says at 1:03:

You're looking for 3 things: Swamps, snow, trees. Your best chance of surviving is to land in one of those 3. Just stay away from water. Whatever you do, don't land in the water!

With

(You'll die.)

being written on the screen.

Is landing in water when free-falling really guaranteed to be fatal?

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  • An interesting albeit somewhat technical persepective is given at http://www.askamathematician.com/2012/07/q-why-is-hitting-water-from-a-great-height-like-hitting-concrete/ – Fizz Oct 28 '17 at 16:49
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    Your question as written is trivial however to answer as "no" because free falling can mean from a few meters. – Fizz Oct 28 '17 at 16:53
  • Related: https://outdoors.stackexchange.com/questions/8106/how-far-would-you-need-to-fall-for-it-to-be-fatal – Fizz Oct 28 '17 at 17:05
  • Here's one of the Mythbusters episodes on the topic (there were at least two actually): https://www.youtube.com/watch?v=E408JigEcFI Landing on the belly in water is not as bad as concrete, but still fatal. Older episode on hitting the water with or without holding a hammer: 200-300g experienced by the dummy, fatal either way: https://www.youtube.com/watch?v=oCSQExxWulU – Fizz Oct 28 '17 at 17:28
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    Swamp _is_ water with trees growing out of it. – Solomon Slow Oct 28 '17 at 17:29
  • And https://physics.stackexchange.com/questions/106808/why-is-jumping-into-water-from-high-altitude-fatal/106814 which has surpsingly weak even if heavily upvoted answers. The only one I've found good is way down the page, even if rather approximate: https://physics.stackexchange.com/a/106860/70429 – Fizz Oct 28 '17 at 17:35
  • @Fizz Water isn't "as hard as" concrete at any velocity. Velocity has nothing to do with hardness. – WakeDemons3 Oct 30 '17 at 22:30
  • Re "Swamp is water with trees growing out of it." I wonder if the suggestion is that marshy grass and saturated muddy ground might be softer than impacting water. I doubt there's data, but that's how I took the OP. – Larry OBrien Oct 31 '17 at 18:23
  • @WakeDemons3: "Velocity has nothing to do with hardness." [citation-needed] – Oddthinking Jan 20 '18 at 00:43

1 Answers1

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It's possible to survive a free fall in water from extreme heights, but it's an extremely rare event, so the conditions for survival are not known. Snyder (1965) mentions two cases of survival following free fall in water after parachute failure:

  • pilot falling from 15,000 feet in the Pacific Ocean
  • sky diver falling falling 2,550 feet into a pond

Drag (thus velocity) could not be determined (by Snyder) in either case though.

After a bit more searching, I think the first case refers to that of Cliff Judkins who suffered a streamer in 1963.

Given that falling a mere 59 meters (~193 feet) into water has a mortality rate of 85%, it's probably not a good idea to try this yourself though. As it was correctly pointed out in the comments below, this statistic is based suicide attempts...

... and it turns out that if you do find yourself free falling over water, Snyder found that body posture upon entering the water is a key factor in survival. His study included survivors only; although the majority of the cases were suicide attempts as well, a few accidental falls were included. He found

  • No correlation between velocity and degree of trauma, but keep in mind all his data was for falls over 52 ft/sec = 35.5 mph, corresponding falling from a height of about 55 feet.
  • Best way to increase survivability in water: land feet fist. Critical velocity in this position is about 100 ft/sec (110 km/h, 68 mph). Unlike falling on a hard surface, no fractures of feet or ankles were recorded in this position; bilateral midshaft fractures (i.e. breaking both legs) were common though, although the most common injuries were compression fractures of vertebrae for this posture. Organ damage occurred in only 14% or cases of entering feet first.
  • In lateral or transverse (prone or spine) postures, 100% of the cases suffered internal organ damage, with renal hematoma being the most common one.

These findings are corroborated by a 1986 review paper that mentions that of all recorded cases (till then) of jumping from the Golden Gate bridge (250 feet high), all cases of survival landed feet first. The mortality rate was 100% for striking the water with the body horizontal.

Fizz
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    The problem with your 59 meter data is that wasn't people trying to make a proper entry into the water and almost certainly not able to, anyway. (They didn't start prepared for a good entry and didn't have time to fix that if they changed their minds.) My understanding is that if you do it **just right** you can walk away. – Loren Pechtel Oct 29 '17 at 05:18
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    @Loren *swim away –  Oct 29 '17 at 05:28
  • @LorenPechtel "changed their minds": I expect that only a trained cliff diver would be able to effect a change of mind with any degree of reliability. – phoog Oct 29 '17 at 21:10
  • @LorenPechtel: fair enough. Unfortunately, I doubt that there exists enough data for the scenario you want (survival intended). I haven't seen any studies of that. – Fizz Oct 30 '17 at 01:11
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    Often cliff divers (ala Acapulco, etc.) time their dives for maximum froth in the water. Air bubbles in the water compress and cushion the impact. – BobT Oct 30 '17 at 03:23
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    I would not be surprised if the pilot or the skydiver incidents cited had a 'streamer' form of failed 'chute. This would slow their fall well below terminal velocity. – BobT Oct 30 '17 at 03:26
  • @BobT The cliff divers are normally going for maximum wave height so they have the maximum depth of water--the big danger is hitting the bottom. – Loren Pechtel Oct 30 '17 at 03:46
  • @phoog Given enough time a skydiver should have no problem choosing their angle of entry, although whether they could do so to the precision required is another matter. (It's slightly offset from going straight in feet first.) – Loren Pechtel Oct 30 '17 at 03:47
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    A discussion of hydrogen bonding, surface tension for water, and the differences between landing on flat, still water and water that is in motion or being somehow churned might improve this answer. – PoloHoleSet Oct 30 '17 at 14:34