You should know that Minecraft falling down from a very high height, water is your best bet from fall damage. But if you tried that height in real life, you just might die.
Anyone that did a belly flop, you most likely got a burn on your stomach. And it hurts very much. Believe me, it does hurt.
Okay, back on track. In Minecraft, if the physics were real, you would take damage hitting the water would take damage and if the water was too small in depth, you would take damage by hitting the ground, and most likely die.
An addition or change was put into Minecraft making water not pass your head first to not deal damage. Or in English, water had to be at least 2 blocks high or more to break your fall. Now it can be 1 block high. This change is not realistic. It is like falling 5 feet into a puddle.
Minecraft water physics are broken. Hope you read this and understand it.
