You actually can't kill the enemies that are flying too high *above water* and other bug I found while playing this is that if u get killed by a boss/mini boss, you can glitch and whenever the boss goes onto the place where you died, it plays the boom sfx in an infinite loop as long as the sprite is on the dead "body" of the submarine.
I liked the game but it's very glitchy. When I clicked 3 for third skill for any char I only got heal all... but when I clicked the skill icon I could normally use the skill for each char and not only heal all.