On the build that I played at the ubisoft event there were tons of ships at sea you could destroy. When I got to notoriety level 3 one of the bounty hunters absolutely obliterated me because it managed to fire 3 or 4 broadsides in a span of several seconds. From what I saw the difficulty of ship combat should be way higher compared to the bare bones stuff in AssCreed 3.
*sigh*
I hate the stupidity of mass destruction of incredibly expensive and rare vehicles in games. Apparently everyone and their grandmother owns an expensive ship in the 18th century, which is easily mowed down by superhero guy.
Why not make ship combat rare and eventful? Make it difficult and strategic, toy with player expectations, and make them unique. Basically just take a look at Demons/Dark Souls on how to make player experiences important instead of this bullshit "ctrl+c ctrl+v" game design.