Played enough of it to complete it :) Pretty basic for now, but has quite a bit of potential!
If you're up to polishing it, I think all that's needed is more types of islands and more fun adventures to be had on them, a little balancing (digging repeatedly until your hold is full of coins feels like cheating, I'd look towards forcing the player to work for their gold) and something to make the combat a bit more tactical/dynamic. Maybe a shifting wind direction giving one side the advantage (shot carries farther downwind, you can sail faster downwind)?