I was visiting my parents over the holidays (Seattle, WA area) and played a new sport called Skwim. It was fun. The best I could describe it would be a cross between Ultimate frisbee and Water polo. Imagine frisbee in the water, but the disk skims the top instead of flying through the air.
I don't really know how big this thing is, but I played it at a community pool. It kicked my ass, which is partly because I am not much of a swimmer. Title Page
That's their site. It's kind of shitty but maybe they will post other places they play. I don't know.