Nice attempt to implement the theme. I like that you can change the player's submarine by clicking.
Unfortunately the controls are a bit clunky. At first i didn't even know how to change the submarine and then i didn't know that i can shoot bullets with the black submarine. What struck me a lot is that when i have to change the submarine, i have to take my hand off the keyboard, which is bad for my general gaming experience.
All in all i think this game is pretty decent. Good work.