Stand up paddling (SUP) was once confined to the sea and flat water rivers and lakes. But as the sport has grown the limits have expanded, and more people are using SUP boards to travel down whitewater rapids. As you might expect, attempting to SUP over whitewater is somewhat more challenging than calmer waters. As such, it should only really be attempted once you have a solid understanding of how to use an SUP board properly. Whitewater SUP boards are generally shorter to allow them to be more manoeuvrable and easier to steer in difficult conditions. .