FGG's
Razor Coast involves seafaring pirates and Polynesian styled islands with multiiple built-in plots for seafaring and island adventures. I actually found Razor Coast to be a lot more interesting for play and better ship rules, than
Skull and Shackles campaign by Paizo.
I think the
Fire as She Bears supplement for Razor Coast, that includes detailed rules for building ships, as well as a system where all the party members are active during ship to ship actions. In my experience, most ship to ship combat rules end up as an activity between the GM and one interested player firing for the PCs ship with a bunch of remaining bored PCs waiting for the fight to end, so they can participate too. FaSB has assigned positions on ship for every PC, and a round by round activity required by everyone during shipboard actions. For example, there's an assigned captain, a lead gun crew, someone assigned to bringing ammunition and powder from the stores, someone to control and alter the sails to speed up/slow down/make hard turns, a ship's doctor performing in action surgeries to handle wounded and get crews back to the fighting as fast as possible. In the FaSB subsystem everyone has a part in shipboard actions, so are a lot more interesting than most system sea battles.
A couple of supplements from Rite Publishing that make for interesting seafaring adventures include,
#30 Haunts of Ship and Shore which is a collection of 30 seafaring related haunts for inclusion to any game, and
101 Pirate and Privateer Traits - which include one-time-use traits and some other very interesting atypical 'traits', aside from more normal ones for PF seafaring adventures. Fantastic Maps
Merchantman is a deckplan for a merchant sailing vessel.
