So it was a fish piloting the sub to save his fishy friends? I don't think I quite understood the premise, but I guess the abstract nature of fish dreaming plays a hand in that.
The controls were fine, but as you said in the description... collisions...
Bouncing off of things was a fun quirk, but the dropping boxes can trap you in place if they fall on you. Blew up all my fishy friends to get out of the glitchy TNT.
I think it's a solid concept for a game, and a few more levels to expand the fishy's submarine journey could make it a full fledged game.
I think it's just GameMaker being silly with sprites, but all the graphics looked squished and pointy. Have you considered using Unity for 2d stuff? You don't get drag and drop programming elements, but it's scripting isn't too hard to learn if you're used to GameMaker.