It could be a war. Or Pirates! ARGH!
Since it will all be on one thread, you'll want to make it somewhat simple. OR! If you want to make it extensive, make a whole bunch of threads and have a list of links at the top for easy access. For example:
Storyline: blah blah blah blah blah
The "Davey's Bones" ship (click!)
Pirate's Cove (click!)
The Colony (click!)
S.S. Victoria (click)
The Open Seas (click) ((And when two different ships are interacting, members of one ship post with one color, and the members of the other ship post with another. That way we don't get confused. lol))