Despite the lack of environment art, I really liked how the game looked! The fish and player sprites are really nice to look at, and there was a lot of subtle details that I really appreciated like the slight bounce when the player turns directions, the air bubbles, the wavy shader over the screen, text animations, etc. A proper environment definitely would have taken a lot of time, so I think it was very clever use of resources.
Also, the player movement felt perfect.