Heh, neat level for a first level, plenty of tricks you already incorporated.
Like the scenery at some spots, especially the final area.
While I love the music, very funky, it feels out of place with the level itself that's more build around slower gimmicky sessions, where the music feels it belongs in a full blown action stage.
Especially with the dark underwater maze, it feels weird to have an action beat pumping.
Anyway, yeah. You got a few neat ideas in level construction, exploring is often rewarded, so I had a decent time. Altough the level can be annoying at times, you sure love spamming the more gimmicky badniks.
And yeah, underwater mazes in darkness, not really fun, especially not in a Sonic game.