That happen to you Online Multiplayer or Offline, or both?
just FYI, in not familiar with the 9700, but i assume its DX9 hardware compatable card.... if you turn CSS to run in DX7 or 8, your FPS will double or tripple, but as a trade of for sepecial effects/image quality.
the command is (mat_dxlevel 70) options include(70, 80, 81, 90)
I dont remember if the game needs to be restarted or not befor it takes afect... but you can input it into the target line of the game shortcut to have it take affect instantly... by right click shortcut icon/properties/target = example ["c:\program files\valve\steam\css.exe" -console +mat_dxlevel "70"
-console enables ingame console to input commands... well in HL2 anyway, not shur it its automaticly enabled in CSS, cause i never played CSS.
EDIT: note you can see threw water in anything bellow DX9 because the special reflection affects arnt there. i hear people turn it bellow DX9 when they go multiplayer purposley just to see threw the water sometimes. those are Hardcore FPS's of course who are after nothing but winning, even sacrificing image quality.