Interplay of Energy Systems
When the person runs from the sand out to the water, the anaerobic glycolysis system would be dominant. This would stay the same when paddling out. They would be working at about 95% intensity. The aerobic system would become dominant after this when the person sits out in the water waiting for a wave. ATP would be resynthesising while the aerobic system would be the dominant system.
When a wave comes, there is a quick burst (0-6 seconds) of ATP as the person jumps up onto the board. When riding the wave the anaerobic glycolysis system would become the most dominant, and ATP would slowly be resynthesising, however when quick moves occur on the wave, there would be a little burst of ATP.