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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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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.

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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, 2017 at 5:18
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    @Loren *swim away
    – user11643
    Oct 29, 2017 at 5:28
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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, 2017 at 3:23
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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, 2017 at 3:26
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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, 2017 at 14:34

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