Berserk.

I don't know if it really needs a presentation due to it's reputation so let's say the anime will feature Guts the black swordsman who got really fucked up due to being backstabbed by it's former friend and must seek revenge by battling evil creatures who chase him with his big ass sword and find a way to cure his girlfriend disease which is close to Alzheimer.
The manga is stuck on a island instead of a boat for now.