The idea is great, the textures are nice. My only problem is, that this game is unfinished. It's need some more update to be an complete game. For example if we could swim up and down with the fish and the shark, it would be nice.
And that would be also great if the shark and the fish were given animations. As an extra maybe you should take some new maps and skins in the game as an extra feature. Than it will be a complete game.
(Sorry if I have some grammatical mistakes, i am still learning English)
Anyway just keep going!