No fall damage taken when landing in water

What I expected to happen was...:
Mobs should die when falling from over 24 blocks into the 2nd smallest stage of water

What actually happened was...:
No damage is taken

Steps to Reproduce:
1. Spawn a mob in mid air, at least 24 blocks above ground
2. Put a 1 wide water stream for the mob to fall in, make sure its at the 2nd smallest stage
3. it doesnt die