As long as where ice is supposed to be it is and where the sea is ice free it is unlike DW where you can be sailing along in supposedly ice free waters and then sink from hitting ice which doesn't show up in any display.
One thing and I think this is to do with physics is how collisions will work. IN DW you bump something you damage until dead, you can be in dock and wave motion makes you bump the dock and you die.
How are you planning to work this in? I know this is in the future but having working tugs would be fun that would back you into position from the wharf or if you have a surface vessel it can ram small boats without inflicting heavy damage in itself.
__________________
|