Using the same Chaos Chest system you could add shipwrecks to the sea (or even floating crates) containing appropriate loot (gold, timber, wood up to map, shipbuilding module or astrolabe). This would lead to having players around the seas hunting for wrecks and players chasing those who hunt wrecks XD
People love boats. But only a couple clans actually own them. Unless you count rafts and launches, of course.