I think I'll agree with OP on this one, it doesn't really make sense for "normal" wild life to be attacking boats. like boars for example, to swim out to specifically attack your boat.
If it's just floating there, it's pretty much scenery to most things.
The way this breaks my immersion, and I think the spirit of the game, is that I will not leave a ship at a beach or river. I will just smash it up and and pocket the parts. even if it is just a short landing, I'm not going to risk it. I have a boat house, which is unused. Instead I use a chest labeled [boats].
The boats are very much an important part of going viking, so I feel we should be able to park it on the beach, they are longboats made for driving up on the beach after all, and go on a fairly quick raid, without worrying about some wild bacon vandalising it.
Especially when the only way to transport metal and ores is by boat.