Stand up paddle (SUP) involves standing on a long board and using a paddle to move yourself across the water. SUP boarding over flat water is probably the best introduction to the sport. Flat water is the least treacherous way to SUP as you donêt have to contend with waves or current. This way you can focus entirely on staying balanced and picking up speed. Flat water SUP boards are usually quite large, but very streamlined to make it easier to cut through the water and move faster. .