when i try to make the scenario file, i get this error

building pvs... two fog planes intersected in a cluster (see black in error geometry).

how do i fix that? (its my first water map)

Your water has the fog plane flag on the material name and your water isn't all level. Remove the $ off the name or remake the water plane to be level.

how do i make it level
Edited by Halocombatevolved on Feb 27, 2010 at 11:28 AM

it doesn't necessarily mean z=n for all verts does it?

you could simply select the entire water plane and use make planer and keep the $ (fog). think of the fog plane as emitting fog like a beam of light, it goes on and on infinitely in one direction (for water this is down). if you have more planes and they're not perfectly planer then at some point the fog "beams" will intersect. you cannot have this.

is it ok that i use a box thats very thin instead of a plain because whenever i use a plain it has 10 open edges

no.

use a plane with only two tris i.e., 4 edges. make sure all the verts and outside edges are outside the bsp.

Add ! to the end of the material name. This makes it non collidable, so it won't have to follow the sealed world rules.