The water won't be too bad if they code it well. Silent Hunter 4 has ocean effects that good, with dynamic wave action, and I can run it at 1024x768 on a 2-year old PC and GPU... a pretty hot setup for the time, but still that old. Might need some major horsepower to run it at really high res though.

Considering how the current AI handles pathfinding for wall assaults, and inside cities, it will be interesting to see how those guys get from one ship to another during a boarding action. I guess it helps that it can't be more than a fairly limited number of men at one time, compared to huge army assaults on cities.