It looks like a manufacturer called http://www.10bar.com/ has released underwater housings for both the Panasonic GH1 and GF1. It appears they are located in Hong Kong, so I am not sure how you would buy one. Possible dealers in the USA. The housings are rated to 300' deep and allow for full control. I am assuming the GH2 would work as well.
http://www.10bar.com/new_home.htm