Chances are that the type of water you are using is wrong. Which texture did you texture the top with?
PS: Here is a tutorial for you...
2fort water is meant to be dirty, so it's fog level is quite close to represent that
Try... lets say... Well? Hydro's water could also work well.
Il make you an example. Itl be up in about 15 mins.
PS: There are no ladders in TF2.
Hammer likes to freak out and cry whenever you texture the sides and bottom of a block with water. A.k.a it won't work unless you get a special material for that sort of thing. But even then it won't really be water.
Tell me you didn't carve that thing in the top-right viewport. Please.
Tell me you didn't carve that thing in the top-right viewport. Please.