Very nice game! I found it fun to play.
I really like the attention to detail that seems to have gone into it, such as the submarine's horizontal and vertical rotor moving individually. And especially the sound effects, they fit well!
Not sure if this game even needs background music. Perhaps a bit more ambience in the background.
It'd be nice if the background color between areas would change gradually, though.
I also think this entry could use a bit more neon, even though it's clearly present in the submarine itself. Because of that, the theme use feels a bit limited.
Nonetheless I did really enjoy this entry!