# Physics: Surviving a fall while suspended in water

Imagine you’re falling from a great height while suspended in a sphere of water. Basically a giant rain drop. Do you survive the impact?

I know above a certain height falling into a body of water is similar to hitting solid ground. The water can’t get out of the way fast enough. In this scenario, the sphere of water can’t go through the ground so it explodes sideways in all directions. I imagine if there’s enough of a crumple zone between you and the ground the energy can dissipate and you could live. Or would the shock wave travel through the water and break every bone in your body just the same?

I imagine there might be a problem with a large sphere of water retaining its shape due to air resistance, but I’m not sure how big a problem this is. Maybe if the sphere is big enough?

Sorry for not specifying any numbers for height or amount of water. I’m just wondering if there’s any scenario where this could help. I’m guessing the drop would need to be at least a couple meters in diameter, but I dunno.

Feel free to make your own contrivances for how this could happen. Maybe a wizard forgot his parachute and poofed in a water bubble around him. Or a James Bond type was in an airborn aquarium or pool and blew out the bottom with a bomb.

I’d guess the shock waves would collapse your lungs and sinuses and there would be strong shear forces which would tend to rip you apart.

Asides from that it’s a plan!

Some physics problems are hard, some are easy. This one is trivial. Water is not (very) compressible.

So when the bottom of the bubble hits the ground, the shock wave will be transmitted almost losslessly right to your body.

And the big bubble of water, since it is 1. Spherical and 2. Big enough for you to be immersed in
has much more internal volume relative to surface area. That means it will have a much higher terminal velocity than you would have if you were falling outside the bubble.

TLDR : you are far more likely to die if falling from the same height inside the water bubble than outside it.

Think what happens to a drop of water when it hits the ground. It splatters. Why would this help you avoid the same fate? As Habeed says, all it will do is make things much worse due to the much higher speed of impact. If you hit a body of water - lake or sea - it would probably act to avoid some of the effect of impacting the surface - but you would still face the problem of decelerating though the water at a velocity much higher than if you were free falling into the water by yourself.

I think the water may help. I think it will decelerate you more gradually as the water under you gets out of the way.

Now, if we could have you in a spherical container that keeps itself together somewhat, like a car with crumple zones, that should help quite a lot. That’s not the proposed situation, though.

And Habeed’s point about terminal velocity is a good one (which I wasn’t about to think of, either). Maybe that’s more important than anything else. So I’m not sure.

Still, I think the water may help, for part of the same reason that it’s hard to slap something vigorously underwater, because the water doesn’t clear out of the dwindling space (though the issue that you can’t get your hand going very fast does not have a corresponding agency in the OP scenario).

An aggregate of water much beyond a raindrop does not hold together very well and would disperse rapidly away from your body while falling. Look at a real world example of what happens to large chunks of water big enough to encompass a human body when dropped from the air.

Water doesn’t crumple. It’s essentially incompressible so it transmits the shock at impact point directly to you at the speed of sound in water.

That’s why water crash landings are described as hitting concrete.

That’s also why throwing a grenade into a pool would probably kill everyone in the water.

Shock waves are bad for you. This lovely video demonstrates what you might expect sharing the water with an explosive.

However for the OP’s scenario I doubt you would ever see a shock wave. To be a shock wave it must be propagating faster than the speed of sound in that medium - which for water is just on 1500m/s. You will not hit the ground that fast no matter what, and thus although there will be a compression wave - and it will be bad - it isn’t a shock wave.

I think being in a large ball of water will help.

It seems to me that the situation will allow you to decelerate over a larger distance than when your body alone slams in a large body of water.

An that will drop the g forces significantly.

And IMO, the shock/compression wave, that even if it exists, just isn’t going to have much ummph.

Now when this helps enough and when it doesn’t and when the faster terminal velocity negates any advantage are details for the devil to work out.

I am not a scientist.

I believe the biggest problem would be the body of water dispersing while still in the air.

However…

If the water could be persuaded to stay in a single mass (without changing it’s usual liquid state - i.e. don’t freeze it solid) would it not be possible to “dive” through it on landing?

I am thinking of the difference in impact felt when diving into water and doing it properly compared to a “Belly Flop” when you hit the water flat.

TCMF-2L

I think billfish678 is on to it, here’s my take.
If I understand it correctly, one of the reasons the brain is surrounded by cerebrospinal fluid in the skull is to help it withstand shock. The brain is spongy of course, but the extra room around it, although minimal, allows the fluid to be displaced and stretches out the time variable in a given impact. More time, same deceleration, less g force overall. Same theory as a motorcycle helmet. So if a person were in a container surrounded by fluid, with room for displacement or shifting within that container they would probably survive the impact better. Drown maybe, but hey…

You might as well attempt to survive a fall while encased in liquid cement. Only slightly heavier than water, and as a liquid, it will help cushion the impact, surely. If you’re really worried, just position your body so you can dive through it. That will slow you down. Just my opinion, I’m no scientist or anything. I have no idea about shockwaves, but in my opinion, there’s no such thing as shockwaves. The laws of physics don’t really apply in a liquid. That’s why we use water balloons to cushion the impact of car crashes, and planes that are no longer in control land safely in the ocean all the time and aren’t torn apart by the impact. I mean, they’re made out of metal, and you’re made out of soft squishy flesh, and they survive the impact just fine. That’s why we can always find the plane intact after it crashes, and they don’t go looking for tiny pieces of the plane that might be floating wreckage, and mistake garbage for plane parts. Because water is soft and compresses easily. In fact, the planes just glide right through the water, like a submarine. They actually end up landing the plane on the bottom of the ocean, the water having safely slowed the plane down enough to land. It’s not like the plane gets obliterated on impact because the water is like hitting concrete. It just moves out of the way, don’tcha know?

Opinions are great. In my opinion, Jesus rode dinosaurs wearing a cowboy hat, and he spoke English.

Water is an nearly incompressible LIQUID.

Not an incompressible SOLID.

It makes a difference.

Yeah, water can’t crumple, but it can splash. The water below you will get out of your way by moving sideways.

I hope there have been sufficient factual answers for me to ask this followup: what if you were in a giant bag of styrofoam peanuts? If there were no limits on the size of the bag, could you survive a fall at terminal velocity?

No. It’s terminal velocity.

I saw this thread title, and thought, “Wait a second, didn’t XKCD answer this precise question with excellent depth and humor?” And yes, he did. But Askthepizzaguy provided the link in post #5:

To those without the patience to click the link, if you fell from a great height while surrounded by a large quantity of water, the shockwave would kill you.

Not sure if Dag Otto is serious here, but if so, he should understand that the “terminal” in “terminal velocity” does not mean the fall will kill you. It just means it’s the velocity at which you stop accelerating. If you’re wearing a parachute, your terminal velocity is eminently survivable. If you happen to be something like a cat, your terminal velocity will sometimes be survivable. If you are dropped from the edge of space in an arbitrarily large sack of styrofoam peanuts, I imagine your terminal velocity would not be very fast, and when you landed, the shock would be dissipated pretty easily. I’m sure most average healthy people would survive, given a large enough sack of styrofoam.

The problem with the Styrofoam peanuts is that your gravitational potential energy has to be converted to some form as you fall. If it can’t be converted to kinetic energy then it’s going to become heat most likely, and that can kill you as surely as the fall (or rather, the stop) will.