Cowabunga dude!
Surfset provides a fun and unique way to get sweaty. Essentially, you are doing basic workout moves but on an unstable surface in the form of a surfboard. The surfboards cater to different balance levels by using bungee cords along the sides to help stabilize the board. In any case, you can bet that your core muscles are working the entire time.
Last night, I tried the "Blend" session along with Jaime W, Angela T, and a bunch of their friends. It was a nice, balanced workout (pun not intended). Most of us were still getting used to the boards, so the workout wasn't all that intense. I'm certain that they can get pretty hardcore once you get your sea legs.
Totally Tubular!