First, I think you should add more fish, and some reasons for player to dive deeper!
Second, its really hard to know that where is the fish, and where is the player, add some background or stat like depth, enemy number, or a minimap will help a lots!
Third, the dash system is nearly meaningless, the fish cant touch you!
But this game is quite fun, I love the gun sound, love the stick man animation! This game has large potential. Keep it up!