Not sure if the Garry's Mod version is different from the TF2 version, but here's a few things I noticed that should probably be fixed or changed in the future.

Half-Life 2 props and textures are visibile. If you really need those, I'd recommend you change the texture and then make it a seperate prop to use. If it's inconisstant in the art style it's very bad to look at. You're using the wrong kind of falling water effect for leaks and it's pasted quite lazily multiple times in different spots. It's clearly spilling gallons of water every minute so it makes no since as to why there's no major flooding. With the amount of water leaking in, this entire map should be completly flooded. I'd recommend removing all of those and replacing them with the dripping water or the spraying water, as those seem much more reasonable and less excessive. The eyes of the dead bodies are untextured. Loose props in the map which could be used to damage players, again, not sure if it's like this for TF2. You may want to rename this map. "Close Encounters" doesn't exactly give me the immediate thought of an underwater city. It may be a BioShock reference I don't know about, but I wouldn't think so as I've watch a playthrough of the game and it's not ringing any bells for me.

Main thing I think should be changed is those water effects. Especially the one coming in from the side of the walkway glass. It looks awkward. The way it's coming down into the building. That's not how water reacts, it looks really unnatural and it's rather distracting. Just use a different water effect. The one you chose was strictly designed for water that's leaking down a wall.