Love the atmospheric, echoey sound to this game. As most physics-based games are, it was a little wonky trying to physically collect the souls, so I just gave up on that and went for the boss kill strat, after reading your comment about its health bar (I also assumed that was something related to the souls).
The boat design is really funny to me, as it's just an ordinary trumpet attached to this otherworldly, ethereal soul ship. The physics of the horn blasts were cool and it was satisfying making the boss whip himself with the green chain. Nice crunchy sound fx for the hits. It's cool you went for full physics design in this.
It would have helped to have some indication of the horn's charge, either with a charge-up sounds or a visual bar filling up, or making something glow brighter so I knew when it's at full power. Going for the attack strategy also made it so I barely had to tilt my ship at all to survive. The jumping sea monster fish didn't really do much to me either, so it was a pretty easy win once I knew I could beat the game from killing the boss.
Great job on the project! Looks like you gained a lot of XP in godot's physics from it. The chain turned out great!