Jump from high enough, and water behaves like something else entirely.
The reason is simple and strange: water is essentially incompressible. The US Geological Survey notes that even under enormous pressure it barely compresses at all, so it can only move out of your way.
Fall from ten meters and you arrive at about thirty miles an hour. The water has milliseconds to move, and your body decelerates almost as hard as if you had landed on something solid.
The water never changes. Only the time you give it does.