Setting Sail: This is a great piece to signal embarking on an adventure. I think you have good pacing with the adding of the different layers, though I really like that final synth instrument and I think it would have been cool to introduce that earlier! I really like how you ended with it though.
Wish Upon a Star: This is such a peaceful rhythmic track that is great for the first level of the game you describe. I like that it uses the same chord progression as the track before and would be able to seamlessly transition at the right point in the game.
Boat vs. Sea Monster: My favorite part of this track are the mysterious arpeggios that emerge at 1:55. I also really like the slow build-in to the next song at the end. So far you have such seamless transitions.
Transformation in the Depths: The low bass drone is reminiscent of deep sea noises while the main ostinato is like many bubbles rising up around the player. This track is perfect to accompany sinking to the bottom of the ocean as it captures the despair and the anxiety of what has happened and what is to come.
Home at the Bottom of the Sea: Interesting choice to go back to string pads since that is what you started the OST with, though starting with the low bass does feel more ominous. I think the choir also gives an other-worldliness to the piece so I think that was a great addition. The siren transition at the end was super cool!
Vibin’ with the Fish People: What a groovy track! There are a couple instruments you use that I think were a particularly good selection. There is a warbly underwater type synth that adds to the environmental sound design which is a great addition. I also really like the panning you did in this song as it feels like instruments are swaying back and forth in the gentle ocean floor currents.
Lair of the Beast: From a compositional standpoint, this captures a very creepy and ominous tone. The piano arpeggio makes perfect sense, but I think that having heavy reverb on the piano would probably add a lot to the aesthetic. Same with the flute. They both sound dry in front of the echoing drones. Otherwise this is a great cut-scene track that conveys detailed emotion.
Showdown with the Sea Monster: The second phase is where the chaos really kicks in! You can tell this would be an intense boss fight for sure. I wonder if use of cymbals in the percussion part would allow you to pick up the intensity even more? My favorite part of this track is the pulsing bass triplets - they add to the chaos subtly and also make the sea monster feel even more powerful!
Home at Last: This is a nice and peaceful track to end on. I like the melodic ostinato while the percussion is allowed to take center stage for this track. Overall this sounds like it would be a really fun game with lots of great musical and story moments. Thank you for sharing!