I heard that you can not survive a fall into water at a height of 250 feet or higher. I have also heard that the reason for this is it acts like concrete at the speed you would be traveling. My example scenario is kinda odd but goes like this. You are a paratrooper. You have just jumped out of a plane and your parachute has failed to deploy but, there is hope because the ocean is under you. If you drop a cooked grenade into the water would it disrupt the water to the point that you could fall into the blast point and survive? My reasoning: 1.What kills you is the sudden stop. So making the impact last longer (with a roll for example) reduces the chance of death. 2.You would still hit the water but, disturbed water is more spread out with pockets of air so it may slow your fall over time and not all at once. Possibly leading to you being able to survive the fall.