Loved it! The chords in the first track definitely give off that underwater vibe, and instantly set a really great tone. I really liked the atmosphere and vibe of the night track, your description of it definitely feels very accurate. I also liked the atmosphere of the deep ocean track. The slight distortion on some of the low chords really gives a nice feel. I think my favorite track was the boss theme. Very different in style from the others, but I think it works really well. I loved the dynamic feel of the melody and the slide on some of the bass notes. The last track was also really nice. I loved the melody and chord progression. The somber tone definitely fits a game-over track.
Overall, I really liked it! (Sorry if my feedback was a bit repetitive, I'm not very versed in the terminology of this stuff.) Great job on this. :)