ok so two things
1. i noticed that the fish always spawn going in the same direction you are facing, except for one fish that spawns in the top middle and always faces right.
2. if you take more damage than you have health,( i.e. taking 3 bullets with 1 health left) you go into the negatives. funny thing is, the games code makes it so you only get a game over if you reach 0 health, and it doesn't account for anything below that. so you can lock yourself into an endless game.
i would also like it better if it was top down, that would make it so much easier to concieve what's happening.
i do like it tho, it is a good concept. i just wanted to point out these things in the code so you could possibly fix them.
edit: after like 2 more seconds of playing i realized that there are three fixed spawn locations and 2 are facing left and 1 is facing right.