This is Vodka - it drops from one of the mobs in the weaponsmith room ( can't remember name, but he spawns next to the rats) we've killed him twice and got it twice
The compass is used in the Captains Room with 3 other items apparently found on board, the Spyglass, the Ocean Map, and "the captains favorite brew". The 4 items are given to the lone guy you first find in the captains room. My group hasnt found all so I cannot say what happens after, but I get the impression it will be heavy combat.