Whacking the waves

They were bunched together, halfway up the beach, judging and assessing the "whackability" of each successive wave. When they judged the next wave was a goer, one would sprint over the sand, holding a boogie-board out in front, and launch himself at the top of the wave. When contact was made, he would harness both sets of energy to project his body into a somersault taking the board with him. Avalon Beach (Pacific Ocean) on the Pittwater Peninsula just north of Sydney Harbour.

Puts me in mind of a rope game from the 50s: two ropes turning in opposite directions, the gamester needed to judge the best time to enter the twirling spaces all the while avoiding being burned on the legs.