Not sure what you mean by that. Z hordes can spawn in the ocean. I had a wave (no pun intended) come from there yesterday. In a previous version of the game, I had built a base at the bottom of a small lake, thinking the Zs could not reach me there. Wrong. They would just wonder down like it's nothing, knock on the walls, trying to share the good news and all. It was safer to engage them there, since they can't swim and I could, but they were harder to kill as ranged weapons don't work as well underwater. Also, there's the whole not drowning thing.