Being unfamiliar with one's surroundings/activities thus often being vulnerable in such circumstances.
Commonly used to describe a change in surroundings by phrases such as 'going fish out of water' or 'to go fish out of water.'
In this sense, the meaning is similar to the term 'Slippin
' meaning to leave one's usual abode/habitat to enter next manz endz.
Brare 1: Yo blud come we roll down (enter endz of choice here), still.
Brare 2: Rah!!! Allow goin' Fish out of Water down dere blud, manz gonna get merked ugetme?!
Brare 1: Oh yes, I suppose you're right old bean. Silly me.