I concur with Cruxx, al I did was swim around and kept shooting.
I wandered around there cause it was unexplored the first time, then I suddenl came in that room unknowingly it was a boss, just having to had the mithalan boss I had no more food items, so I had to do my best, lol.
Same thing with the octo, had no food, kind of stressfull actually, make sure you always have enough food. I didn't, it sucks.