Cargo Hold is one of the two locations in the map that is filled with water, you can drain the water as on the right side of the pack a punch machine (if you're looking straight at pack a punch) you'll see a valve on a pipe on a wall, press 'X' and the water will eventually drain. You CAN do this achievement while in the water but i'd highly suggest you drain the water as you'll have an easier time.

All you have to do is survive within the cargo hold for 5 consecutive rounds, so say you got in there for round 9, you'll need to survive round 10-14 in order for the achievement to unlock, if you do leave the room before you unlock the achievement it'll reset and you will have to survive the full 5 rounds again.

I'd suggest doing this on easy difficulty, with the pack a punched Kraken as you can comfortably survive anywhere with that OP weapon for 40+ rounds.

*NOTE* Achievements can't be unlocked if using modifiers, when going for achievements use classic!

Worth 15 Gamerscore.