You can do the "swim" ability if you use latest efx mod, but if you can't wait I think I remember that update 1.17 will have the ability to change gravity and use a jetpack, so with that and changing some animations of the weapons you could pull off a good "swim" effect like say far cry. As far as 3d water effect you could use
this made by HockeyKid and Red Eye for what fpsc can do now. It maybe just huds and fog, but it will just take some effort to pull it off. If you close to something and have some problems with the scripting, just ask for some help and maybe if you are lucky maybe Ply or Hockeykid will shed some light on it. I know Ply had
this on youtube, so he is and I think a couple others have actually pulled the water off in some test, but they are not stock fpsc, they are mods.
But if you would like to see more water in fpsc stock and modded, here is what I found:
http://www.youtube.com/watch?v=VBS9ksyA2lU&feature=related
http://www.youtube.com/watch?v=LfhktEScElM&feature=related
http://www.youtube.com/watch?v=Pg25AaLcYnQ&feature=related
http://www.youtube.com/watch?v=GE1VLlusohE&feature=related
http://www.youtube.com/watch?v=9oTjB6sTFZs&feature=related
http://www.youtube.com/watch?v=7BLLXMrMWuA&feature=related
http://www.youtube.com/watch?v=PqxMbvCWuG4&feature=related
I hope this helps and remember searching is your friend. If you need more help just ask, I will do my best to point you in the right direction.