The company called Aavid wants to water-cool a lot of R600 cards. ATI is telling its partners that this is an optional stuff and that you don't need to do it, but the water cooler is there if you want it.
The water cooled card will be overclocked as well but no one knows the real clocks. Obviously this card will be more expensive and faster but there will be market for it.
Asetek also has its water cooler for R600 and this one should do a good job as well. ATI's Add in board partners are working on its water cooled designs and some of them might be ready till May, till the launch time.