Great job submitting a game! This is a pretty ambitious project so big props for making something like this playable in such a short time! I liked the playable tutorial and the cute music. Its awesome you were able to make the song feel like a sea shanty with the sound restrictions. The door to start the game in the tutorial should have a label because I wasn't done reading/messing around and I accidently started the game.
I really enjoyed the gameplay loop. The objectives encouraged exploration to upgrade the ship which let me explore the more dangerous territories. Upgrading the ship was really satisfying since it changed the sprite. Seeing the treasures/crew/map on an island and then searching for the dock was fun. For visual clarity I would prefer the ocean to be blank white with some waves. The dithering gave me a little headache. There were some noticeable bugs I encountered like a dock not unloading me onto the correct one, crew I already interacted with before a ship upgrade didn't want to join even after upgrading the ship, and the M bug in the tutorial section. But with something this ambitious in such a short time I would expect a few bugs.
The kraken boss fight was also awesome. Its unfortunate the surprise got spoiled by the M bug haha. I had fun and I always love a good sea/pirate game. Thanks for participating!