hahaha, me and my friend played like the first half of the campaign over a month, and beat the rest starting from the fish in a single night.
I really do like the cover system, since you have to take cover or u will die, so you need to think abit.
although fights can be abit extended if u cant seem to hit them.
Having trouble on the fish mission?:
saw off the tentacles as they approach, and shoot the eyes when it tries to drag you down when it bites the ship. After that it'll comeback, shoot the eyes and it will open its mouth, run in quickly or you will die. make sure youre past the teeth
grab the nades in its mouth. You'll see 6 tentacles inside its mouth, shoot the ones that are blue. After shooting a few of them, its inner mouth will open up and you chuck 'nades into it. Then you'll be spit out, and you have to repeat the process 2 more times.