This is one of the easiest fights, since the only two things that matter are how fast you switch to Hammerhead and fire it and how close you are to Redbeard for the final torpedo hit.

Like all missions you can buffer switching weapons and targeting the enemy while the screen is black and the game will buffer those actions to be done instantly when it can. So when I hear the beeping sound, I press X/C to switch weapons and E to target the enemy.