I think I found all the endings (good, bad, and secret)? I like the idea of the two different mermaid guides with their different advice. This was a great short and sweet execution of that concept, with the only thing really missing being sound.
I found the ship motion to be very funny. The way it goes upsidedown is perfect and iconic. I don't know if it is so silly on purpose, but for a Trijam game where everything must be made quickly it really works to add a little fun to the game feel.
Once I figured out shooting the cannon, it was easy to crush my enemies. Without sound and with the camera so close I would often kill things without seeing them, and I only knew I'd shot something because I'd already seen what enemies should spawn where. Sound would help the player understand what is happening when shooting enemies offscreen.
The hit boxes don't quite match the visuals, which is common in games made quickly. It becomes part of the player learning curve and expectation, in this style of game. The gameplay loop was fast enough that if I died to a spike that had a bigger hitbox than I thought, it didn't interrupt my play because I could immediately return to it and know to give it a bit more clearance.
All together I think this is a great submission!