Very nice melody !
I agree with RavenBlueIndigo and TheSlowly. I think it's because of the choice of the instruments on the second part. For me woodwinds (clarinet and flute) sound aerial. It's hard to play flute underwater :D
To correct that, maybe if you put reverb on those instruments it could sound more distant like the sounds underwater. I hope I'm clear...
About the composition, I like the 3/4 metric very clear at the beginning. I find this part waterish (like the water worlds in Super Mario Bros).