No, this is no joke or a counter-posting to my wrong-clipping-of-water-surface thread.
This is simply the next problem I ran into when messing with fog in my map.
After I solved the problem with the clipping of the water by a worldspawn fog I found out that this makes framerates drop amazingly if not horribly (down to 25 in too many places in the map). So I wondered what was used in the original map and found out that its a fog in the sky… using these parameters:
fogvars ( .4 .4 .45 ) 4850
skyfogvars ( .23 .23 .24 ) .05
I got a nice fogclipping on the water as u can see on the pics, and for the first time serious improvement on the framerates too: in a standard-bad-spot a raise of about 10FPS (38 without fog, 25 with worldspawn _fog, now 48) and general improvement in the whole map. Only problem is the clipping of the terrain now…
I know GoGerbil worked with a similiar fog once, (http://www.splashdamage.com/index.php?name=pnPHPbb2&file=viewtopic&t=9090&highlight=fogvars) but tbh I didn’t understand much of his thread 
my approach to the water-clipping-problem was already pretty ballistic
edit: forgot to post a terrain-shader… they are all the same (some with landmines and phong, but not all of them). I got 5 terrain-textures (but I doubt this is important).
textures/river2nd_t/terrain_0
{
q3map_lightmapsamplesize 64
q3map_lightmapaxis z
q3map_texturesize 512 512
q3map_tcGen ivector ( 640 0 0 ) ( 0 640 0 )
{
map textures/river2nd_t/rv2nd_rock_steep.tga
}
{
map $lightmap
blendFunc GL_DST_COLOR GL_ZERO
tcGen lightmap
}
}
textures/river2nd_t/terrain_0to1
{
q3map_lightmapsamplesize 64
q3map_lightmapaxis z
q3map_texturesize 512 512
q3map_tcGen ivector ( 512 0 0 ) ( 0 512 0 )
{
map textures/river2nd_t/rv2nd_rock_steep.tga
}
{
map textures/stone/mxrock3_a.jpg
alphaGen vertex
blendFunc GL_SRC_ALPHA GL_ONE_MINUS_SRC_ALPHA
}
{
map $lightmap
blendFunc GL_DST_COLOR GL_ZERO
tcGen lightmap
}
}