I had more or less an idea of what to do but with the limitation my mind went completely blank. 
I'm still looking for something to inspire me but so far it's been difficult.
Anyway, good luck to everyone! See you in less than 72 hours :)

Yea! I am searching for ideas too. My brain just isn't helping me today. I'm having ideas like a bunch of fish being mad at a shark and trying to kill it. Currently I think all my body parts are the fish and I am the whale being attacked by fish :( (its a bad joke forgive me. As I told you, my brain isn't working)

Ayy. I got an idea: You're trying to finish a puzzle, but the last piece is missing. You go to the basement to find it. But it's full of attacking spider's and other creatures. I plan to make it a rouge-like and at the end, you might find the puzzle piece.

Please tell me if it's good or not. I really could use some help here.

(btw if you want to steal my idea, you're free to, but you probably don't want to)

Here are a few ideas.

You play as a scuba diver looking for the smallest sea creature in the ocean.

You play as a fish that has to eat as much other smaller fishes using the smallest number of moves possible. Propel your fish using a slingshot effect.

You play as a creature that needs to get up to the surface by catching a ride on other sea creatures. Try to reach the surface with the least number of hops or falls.