Stand-up paddleboarding (SUP) is taking the world by storm for good reason. If you don't know how to hang ten on a surfboard, SUP is a great way to build up your balance and flexibility. From strong arm strokes that power up through your core to the balance and strength training your ankles, legs, and thighs receive, stand-up paddleboarding gives your whole beachy bod a serious workout. A few of our favorite Hollywood A-listers have even been spotted making moves through the waves on a stand-up paddleboard. Check out who's down with SUP!