I find it hard-pressed to find a doom map i like that doesnt have liquid in some form. Sure, there are maps that are as dry as a bone, but most maps i have encountered (including plentiful iwad maps) bound to have water/nukage/lava/(insert other liquid here) in there somewhere. Why? My guess its that water flats and textures are mostly animated, so it makes the place vibrant. Or its that water is important to our lives, so we just subconsciously include it? JUST WHY?