buckbasin

If the water isn't deep enough to extinguish flames it's usually a good idea to represent this visually so that players don't complain, or run off into the water rather than for a medpack, only to end up dead from afterburn. Allowing the players to still see the floor through the water is one way of letting players easily realise the water is not deep enough for them to swim/extinguish themselves in.

Also, it's probably worth using just sporadic puddles rather than whole 'planes' of water. People are gonna get the message of your theme through the map name and excessive use of mud displacements. Hopefully there's a mud texture that uses the mud footsteps sound, because that would be perfect for you in relaying the boggy nature of your map to players without having to saturate most of the floors with the presence of water.

Also, in this pic: http://dl.dropbox.com/u/1419265/pl_trenchfoot/pl_trenchfoot_a10003.jpg

The only way for people to cap the payload here is to stand directly infront or behind it. Which makes attackers very vulnerable, and susceptable to explosive push back/airblasts that knock numerous cappers completely away from the objective.

If you need a mud footstep sound, the sound that plays when you walk on top of other players is pretty similar...