I like this! Some feedback:
-If you're in the air and stop holding a movement, you slow to a stop. If you instead hold the opposite direction, trying to air strafe, you keep moving forward. This was really frustrating.
-In the puzzly sections with the lever, if you miss the lever you have to wait to drown to restart. It'd be a nice quality of life change to be able to restart yourself.
But lots of things were done well too!
-Ignoring the air control issue, the controls feel good. The rat seems responsive and handles well. I feel an urge to try and speedrun this!
-Rat
-The start and end screens have great art
-As a platformer there's lots of open design space which can be used to expand upon the idea
-It's got rats