The bossa nova rhythm in the first track has me sold. Nice orchestration in the accompaniment, and the lead flute sits well in the mix. The occasional bubble-sounding SFX is neat too - ties into the theme nicely.
I love the vibes in On the Water - great choice of pad. The acoustic dubbed melody is nice and the introduction of the minimal percussion was good to cement the rhythm. Nice wave SFX here - feels very organic throughout the track until the submersion at the end.
Underwater Waltz sounds great - good rhythms and cadence, and the choice of voicings here is great for a waltz theme. Having the bubbles sync up with the beat was clever and it sounds great in context.
Tsukiko may be my favorite of the bunch - the lushy, dream-like vibes at the beginning are so crisp, and modulating the tempo in that second section was a neat touch, along with having the lead square melody blur out through filtering as the wave SFX give way to the gulls. The full send into the old-school chiptune outro was great and returned to the roots of the underwater theme.
Great job, this was a fun listen - some cool concepts in here and the thematic SFX was placed well throughout. :)