Hey I recognize this person!
1) Haha that vibraslap xD, although I would put the volume a tad bit lower myself. That jazz-piano (or whatever it is) starting at 0:25 sounds really water-y.
2) Haha, love the bubble sounds at the start. How did you make those? Also love the 3/4 time signature. That "muffled" filter really works like crazy! Those cabasas, the reverb, and the fading in-and-out strings also make it sound perfectly underwater.
3) Simple and fun. Works perfectly for a town theme. I like the steel drum in the second part - I've fallen in love with that instrument as of recent.
4) Would fit well for a platforming section. As you say it: fast but not too fast. It ain't boss-level energy, but fits well for a platforming section. Love the tremolo-marimba at 1:02, and the melody at 1:10 is also great.
5) Would fit fine for a pause theme. I have never been good at pause themes, but this works great!
6) Love the speed-up! I see how you intended it to be a bit slow actually, contrasting the speedy start, though I was really hoping for a banger of a battle theme.. :'). Still, great song!
7) Ahh... peaceful. A nice one to finish off with. The harp also fits well.
I like that you went for many songs, but with many of them being on the short side. That is perfect! It is exactly how I want all entries to be: it would take me ±10 minutes to rate, not much more like with some other entries, and I can still hear a good variety of songs covering wide aspects of the game.
Also, I am definitely going to use this as inspiration for my own underwater music - I've been lacking in that regard and you seem to have the keys to success! Really, I love this :D
Oh, I still have to watch your animations! I always download the songs and listen them from my iTunes. I'll watch it soon :)