I made a glass box with water to put some axolotl's in and some fell out. plus i had no leads, so as a result I had to kill them as the box was 6 or so blocks above ground level ,but when I went to them they started to hover upward as if they where trying to swim to the box. this made the hit box act as though it wasn't there sometimes a attack would land but most of the time it wouldn't. it makes them act as though they are swimming but there on land and not moving an inch except for drifting an inch here or there. most the time you have to get super close to it to hit, unless your lucky and and it just works normally. I tested it in creative to and it also glitches in that gamemode. for some reason it seems to happen the most if the axolotls on wood, but if the axolotl is on grass there seems to be no problem. I have no idea if it works with any other blocks though.

to reproduce:

-make a body of water above the ground

-put wood beneath body of water

-have a axolotl fall out

-get rid of any water accessible to the axolotl

-some time it will happen on wood with no water above the axolotl but it is easier to hit