Was actually minding my own business for once (after the first galleon sink, it was a solo player so we don't count him) and I spotted a Brigantine headed for me so I snuck off with the loot in the rowboat and let them sink my ship. I sold and tracked them back down and attempted to ambush them but they scoured the island due to the mermaid being present and eventually found me. Annoyed but determined I went to the final island in the mission and ambushed them there, this time successful.
I primarily play this game not as a pirate but as a ghost or assassin. Often my goal is to ambush players well within their own territory without the aide from my ship and remain hidden until I am ready to be seen.