During the nuzlocke challenge, is water considered a new area?

I really need a water type pokemon and I've went to area I can access so far and caught pokemon in tall grass, but now that I have an old rod, I can get some water type pokemon but Their is water that I want to fish in, at places that i've already caught pokemon. So, can I catch anything that comes out of the water if i;ve already caught something in tall grass in the area??