I did it is easy how did you not beat it . But i will tell you how to beat it so go through the sunken sub as soon as you get spawned into the game go all the way through it take a right then take another nightcap going dodge the rudders and shoot center item then tack a left and the guy at the end at tunnel shoot him Keep going shoot the ships you see and dodge mines and you got it

try one of the available walkthrough guides:

actually, try several. different authors may describe things a little more in detail or more clearly than others.

good luck!