Overworld Theme: Such soothing piano arpeggios. You also have a really nice full sound that completely immerses me in the underwater vibes. The glockenspiel melody keeps the mood free and light. I really like how you use the cello as a countermelody instrument rather than as a bass exclusively.
Underwater Waltz: I think it’s really cool to have variations of the same theme for above and below water. I think it’s awesome as the composer that you evoked the underwater sound so well with just a few instrument changes.
In and Out of Water: Way to show off the adaptive nature of your music variations! This is really creative!
Menu Theme: This is a nice subdued version of the main theme. The mallet instruments are very pleasing to listen to. I could stay on this menu for a long time just vibing to this track!
Adversity Theme: This would be a great “prepare for combat” theme. The whistle is a fun touch that vaguely reminds me of Wario Ware types of goofy musical elements.
Overall: I purposefully didn’t look through the comments, because I wanted to guess your inspirations without cheating! Your gameplay ideas sound like the types of games I always loved to play like family-friendly Nintendo games. The immersiveness and instrument changes for underwater make me think of Super Mario Galaxy or Super Mario Odyssey. The piano accompaniment, high mallet melodies, and waltzy qualities actually remind me a lot of Kirby’s Epic Yarn which is my guess as one of the inspiring soundtracks for what you’ve made! I like the creativity of the variations on the theme you made and the nuanced decisions you made for each add to the quality of each track tremendously. Great work and thank you for sharing!