"BEWARE HIRING WITCHER GERALT OF RIVIA - DEVIANT HAS BEEN KNOWN TO STEAL BOATS ON TOP OF HIS PAY."
^^ spit my drink.
One of the many under-rated improvements from one of the patches (I want to say 1.06) was when they added 'reverse' to boats. Before that, and before I learned to sail.... whenever I had to sail somewhere, once I arrived I would literally crash land all boats into the docks, yelling 'LAND HO!", and "WATCH OUT!". Adding the ability to 'back in' was a godsend. (and yes, I questioned how the eff does reverse work for a sailboat, but then I remembered.. AARD! Geralt = Dumbledore)
But as far as damage goes, I would purposely sink a boat if it had any damage. It pissed me off. Especially when I took a week to loot every smugglers'-cache (I do not use fast travel). My Kaer Trolde harbor is filled with sunken sailboats, and nobody has said anything to me about it yet. But they do respawn, damage-free, after a couple days. So that system worked.
Just remember, that Witchers are not real sailors. They are cheaters.