Device: Samsung Galaxy Grand GT-I9060
The game detects fall damage regardless of player's speed.
Falling in water will deal higher fall damage than a similar fall on-ground if the player did not lose his momentum.
Ladders suffers the same problem; sometimes, three-blocs high ladders will cause severe fall damage.
Sometimes, LAN guests will suffer fall damage when connecting, eventually killing them.
This bug is present since one of the Beta builds (but I don't know which exactly) and only affects guests in LAN games.
This bug report is a duplicate of MCPE-8552. Please provide your information there to help out.