Ocean waves, like wild horses, are an exhilarating, life-affirming ride that's safest when saddled during the new moon. Tame free-flowing torrents with today's Groupon: for $20, you get $40 worth of surf and skate apparel and gear at Proof Lab in Mill Valley.

With a stylish expanse of brand name products, Proof Lab outfits aspiring boarders with all they need to dexterously maneuver decks around watery and cement-covered bodies. Prepare for a day of carving through waves with rental of a surfboard and wetsuit ($40), or flex bristling arm muscles without swapping bodies with Mr. Universe by renting a standup paddleboard ($40). Proof Labs' surf and skate swamis carry threads from Patagonia, Volcom, Quiksilver, RVCA, Hurley, and Billabong, as well as designer shades to shield eyes from half-dressed pipes. Equip surfboards for the fall swell season with a new traction pad ($22–$38), and keep toes toasty with an aquaiferous pair of O'Neill or Xcel surf booties ($40). In addition to hosting regular demos and outdoor events, Proof Lab makes connections with local skating societies by granting budding sky artists free access to their indoor skate park to test new boards, practice tricks, or recreate scenes from Xanadu.