This was quite fun! I liked going around the seas and finding different cities to dock at and discover. The upgrades definitely were a nice touch, as it made each voyage feel like progress gets made, no matter how small. I think the art and music is pretty good, too.
The idea of ship battles is cool, but I didn't invest a ton into firepower (not many cannons), so the ship fighting felt a bit shallow; maybe that could have its own "battle phase" as opposed to the traveling style of gameplay here. I also ran into a strange bug where enemy ships could chase me on land, which was interesting; not game breaking, but it was funny.
I enjoyed this game a lot, and would love to see another iteration of the game! Maybe you could trade goods with other cities, or the map is even larger and you have multiple travel options. Well done!