I understand your feeling of underwater but i get the impression of being on top of the waves soaring around clearer in my head. looking out onto endless ocean and knowing you can choose any destination, the song makes me feel free and open.
The intro is very distinct and iconic, it stands out and i personally feel it doesn't sound repetitive at all.
the main melody has a beautiful sweeping effect, everything melds and go together. when the intro returns it feels in place with everything else. however maybe it can go somewhere else? a little drama at the end or different beat to separate it.
I did really enjoy this piece, keep it up :-D