# question for anyone who dives / swims



## Wynnara (Jan 20, 2013)

As I'm a wheelchair, there are certain things out side my experience that I kinda need help with. I can swim in a limited fashion, but I have some questions relating to diving that I could use some details on. 

And by diving, I mean a scenario like this...








Assuming a character is a regular person and not an Olympic diver and that the water is deep enough that they aren't at any risk of cracking their head open on impact, how high can someone safely jump into the water? 

Also, I've heard that when you jump into the water from a great height, the impact with the surface becomes a factor. I imagine if you belly-flopped you'd have the wind knocked out of you, but what about a feet first impact? Would generally head first or feet first be more advisable from a great height? 

Lastly, is there any risk of the person being momentarily stunned for a moment when they hit? What would the sensations be just after they hit the water? 


Thanks so much!


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## Steerpike (Jan 20, 2013)

I've jumped from higher than what is shown in that picture with no problems, though after the first jump you learn to keep your legs pressed together because the water will slam you right in the crotch otherwise, and that doesn't feel so good.

I think people can jump from 100 feet or so without much issue. I've never done a head-first dive from great heights, so I'm not sure how that would feel. Feet-first, from maybe 50 or 60 feet, which is what we were jumping from, you get a nice freefall sensation for a second and when you hit the water the first sensation (at least from my recollection) was the feeling that you're really going way under. So almost right the instinct was to try to stop the descent and surface. 

We also went through the top layer of water, which was warm, to a cold layer underneath it, and that was a bit jarring the first time. If the temperature difference were drastic enough maybe that could affect someone; I don't know.


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## Butterfly (Jan 20, 2013)

The weather conditions and type of water is also a major factor. I've heard it said that if you were to jump form the Severn Bridge hitting the water is just like hitting concrete due to height and velocity. That's about a 100ft into a river.


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## Steerpike (Jan 20, 2013)

Yeah that makes sense, Butterfly. I think the record is around 170 feet. Maybe even at 100 feet you'd have to know what you were doing. The place we jumped was right around 50 feet, I think. The measured jumping area below it was 35 feet, and we climbed up a rock and out onto a tree limb growing above that, so 50 feet is a good estimate. No one got hurt or anything, but I certainly wouldn't want to do a belly flop from that height. None of us even had the nerve to go head-first.


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## Sheilawisz (Jan 20, 2013)

Something very important is that you need the water to have some movement, because if the surface is completely quiet and motionless then it will offer more resistance and you could get hurt at the moment of impact.

I think that a feet-first fall is more advisable when you jump from very high (unless you are an expert diver, then arms and head first would be better!) and maybe it would be relatively safe to jump from as high as forty feet. I believe that a hundred-feet fall would be really dangerous, even for the experts...

About what it feels like, I don't know but it must be a real rush of adrenaline!!


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## Wynnara (Jan 20, 2013)

Great guys, thanks so much for this. 
And the characters would be jumping into the ocean so the water would have some movement to it.


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## JCFarnham (Jan 20, 2013)

You know when you watch a diver on the olympics or something like that? The shape they form just before impact is the best way to avoid any of the troubles of impacting the water. You want the smallest surface possible to impact the water first and counter act the tension of the water. Fingers or pointed toes, if possible. The further you spread yourself the more chance of something getting hurt (crotch, biceps, stomach, etc.) 

A competitive swimmer dives slightly differently. We try to enter the water in much the same way as a diver would, but the forward momentum is much more important. So you try to slice in at an angle. Again, get it a little wrong and you belly flop haha. Not fun.

(Aside: it's quicker to swim underwater than it is to surface quickly and carry on. Which is exactly why guys in the olympics swim so far out before surfacing. They even brought in a rule saying you could only go 15 metres, because people were going the whole length and winning too easily.)


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## Wynnara (Jan 20, 2013)

Hmm... next question, although this one is a bit harder... let's say you're on standing on something that's falling straight down toward the water... if you were to dive from it--presumably to get clear of the impact of when the platform hits the surface--would you say the max dive-height starts from the height the thing was at when it started falling or the height when they dive off it?


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## camradio (Jan 21, 2013)

Not 100% sure but one thing to consider with that would be the speed at which the object falls. First of all if the person is not holding on to it or strapped in or something than the object might be falling quicker than the person. Assuming that they are firmly on the object, do from the fact that the two things combined are heavier they will pick up speed.


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## Steerpike (Jan 21, 2013)

Heavier objects don't fall faster. All objects are accelerated by gravity at the same rate. Something light can be more susceptible to things like wind or resistance of the air, particularly with enough surface area (think of a feather, for example), but heavier objects are not accelerated more quickly by gravity. If you drop a 25 pound weight and a 100 pound weight off a building together, they fall at the same speed.

Wynnara - the person jumping off of the falling object is still going to have the momentum they had while on the falling object. Maybe they could counter it a little bit if they could jump up, away from the direction of the fall, but I think it would be negligible. You'd have to figure it from the height at which the object started falling because the person on the object started falling at exactly the same time.


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## Telemecus (Jan 29, 2013)

I have personally jumped off a cliff of between 95 and 100 feet. The sensation is just like jumping off a ten foot cliff... until you brace for impact, and you realize you are still insanely high up! You cross your arms over your chest, and tuck your chin without sticking your head out. On impact, you realize that it really really really hurts your feet (we always had to wear shoes, which helped a little) and then you get splayed out in all directions from the force. You gather yourself as fast as you can, and head up as fast as you can to the surface, since the wind got knocked out of you, and your lungs are burning. It is a rush, but not one I can work up the courage to do often. Hope that helped!


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## Bman10119 (Feb 6, 2013)

I'm not sure if I'm remembering correctly but I remember hearing the different heights of diving into an ocean. Anything below 50ft is fine, after that it hurts like hell. 80-90 causes broken bones and internal damage. Anything greater causes death.


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## Nihal (Feb 6, 2013)

Actually, you can jump from... 164 feet (50m) and still survive. Not that it's going to be easy.

You're going to break your legs and hips and probably other things too, the feeling is of hitting solid ground. Many years ago an oil platform burnt in a terrible fire and some people threw themselves at the sea, trying to survive. It was a 164 feet fall and they actually survived.


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## Kahle (Feb 27, 2013)

If you were on a falling object, say a mast of a ship, you have maybe a matter of seconds before your balance and reactions are gone. The ideal moment would be around a 45 degree angle (sideways fall) and jumping out to put as much distance in between yourself and the object. Larger objects can cause short currents that pull everything else down with them. Also there is the risk of becoming tangled in something like the lines of a mast. However, composing yourself so that you enter safely from such a fall or jump would be tricky


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