OK just to ignore everyone who seems confused about shore damage....

@OP
Are you saying that out to sea just during a save pause that the boat takes some mysterious damage from nothing?


If so then you should try a file verify
Library
with game off
right click game name for Properties
Local files
Verify

Are you playing on a server or solo?

Are you playing in a modded game?
Have you ever used mods even if you don't use them now?