Stand Up Paddle Board:

Stand up paddle surfing (SUP), or in the Hawaiian language Hoe he'e nalu, is an emerging global sport with a Hawaiian heritage. The sport is an ancient form of surfing, and began as a way for surfing instructors to manage their large groups of learner surfers, as standing on the board gave them a higher viewpoint, increasing visibility of what was going on around them - such as incoming swell.

Great exercise, easy to learn, it's a lot of fun!