If you are on a boat with others you are basically boned.


You will spawn in the water where the boat was when you logged out. In those cases you can recover by swimming until your stamina poops then log out and back in.. your stamina will restore and you can make it to shore and hope it isn't a biome you are not ready for.

Other than that you are just not there so no danger in you getting killed if you log out / close game.

If you are on a boat by yourself just jump off the boat next to it to freeze it in place and log off in the water by the ladder..