So I played this five-player game of Seaside a couple days ago:
Haven, Lighthouse, Native Village, Pearl Diver; Ambassador, Fishing Village; Cutpurse, Island, Pirate Ship; Merchant Ship
There's a lot of cool synergy in this board. In a many-player game Pirate Ship becomes more valuable because each time you play it it has a higher probability of hitting someone. And ordinarily if you're going for a Pirate Ship strategy you want a lot of Pirate Ships, so you can play them more often and build up their value faster (Fishing Village will help with that!). But of course in a five-player game you can't get a lot of Pirate Ships, since there's only two per person to go around anyway. And there's a lot of +$ actions, so maybe you can get away with a non–Pirate Ship–based strategy anyway. At the same time, Ambassador becomes a little dangerous to use, since passing out Estates with it can empty a supply pile very quickly and end the game before you're ready.
What I ended up doing was opening Pirate Ship / Fishing Village and constructing a very thin deck. Obviously everyone else's Pirate Ships did a good job of trashing my copper, and after the second or third reshuffle I picked up an Ambassador and finished the job for them. (I Ambassadored a pair of Estates once, but left the third in my deck because I was worried about premature pile-emptying.) Also, the large number of Duration cards meant a lot of them would be regularly missing reshuffles, reducing the effective size of the deck; as a result of this, by mid-game, although I only had one Pirate Ship I was able to play it almost every turn, compensating for my inability to get more than one. Once I got it up to $4 I stopped attacking with it, and together with my Fishing Villages and one Merchant Ship I started having $8 hands regularly. When I didn't have $8 I'd buy an Island to clean out my Provinces and keep the deck running smoothly. I ended the game by noticing there were only three Islands left in the supply and Ambassadoring them to empty the fourth pile.
