Some thoughts: Maybe make it so that some fish start gnawing at the net and the player has to click on them to make them go away to add to the difficulty.

Also, perhaps make it so that you have to click on the bubbles instead of being able to pop them by just holding down the left mouse button.

Overall: The game was very simple but also strangely addicting. I think with some more work put into it you can have something that's even more fun.