Even watercooling a Geforce3 is overkill, dont even get me started on watercooling a TNT Vanta!
Really tho, my advice to you, either get a WAY better video card, then maybe it would be worth some serious cooling, or just leave it as is. Even if you did spend tons a $$$ for watercooling, you would get about 25MHz more outta it, thereforce giving you about an extra 5-7 FPS. Do yourself a HUGE favour, spend the video watercooling money youve saved, and buy a Geforce2 Por 64mbDDR, or if possible, a G3.