Very cool mechanic(the swimming). The idea 2D/3D enviroment is cool. But it feels emty, put some other living things, ocean is full of live, some plants.
Edited because i didn't see you were also in the jam! 100% agree with you, I didn't have time to add it but i still wanted a big open space to swim around in. Ill update it when the jam is over, there is a lot of stuff i had to leave out