A surfer's biggest challenge? Picking the perfect wave

The waves at the Tsurigasaki Surfing Beach are getting bigger and more powerful by the day, but picking the perfect one to surf their way into gold medal contention is proving to be the biggest challenge of all for the Olympic competitors.

Seven-time Australian world champion Stephanie Gilmore saw her dream of emulating her gold-medal-winning hero Cathy Freeman dashed when she fell behind to South African Bianca Buitendag and was left waiting in vain for a winning wave that never came.

The half-hour Olympic heats are mostly spent bobbing around in the water, waiting. Pick the right wave to perform on, as Buitendag did, and it will see you through to the next round - miss it, and your Olympics could be over.

"What they're looking for is a set wave, the bigger waves ideally," New Zealand coach Matt Scorringe told Reuters. "The smaller waves are usually more gutless and have less energy, and it's not as easy to surf strong on them to get the scores."

"Speed, power and flow of the wave are part of the scoring criteria, and they're also looking for a wave that's got a long wall on it, so they can get multiple maneuvers and a variety of maneuvers on that wave - obviously today, that's pretty tricky to come by."

Each surfer's top two waves contribute to their final score, and a priority system ensures that they take turns in having first preference about which waves to pin their hopes on.

"There's a lot of waiting around with priority, to try and make sure you have that priority when that wave comes through," Scorringe explained.

"Other moments when you don't have priority, you might try your luck on some smaller ones - you've got to live and die with those moments," he added.

New Zealand surfer Ella Williams found herself in a similar situation to Gilmore, falling behind to Costa Rica's Brisa Hennessy in her last 16 heat and desperately searching for the wave that would get her back in contention.

"It is a waiting game, sometimes you just have to sit and wait for the bigger waves, it is a bit of a risk. Sometimes it pays off and you're like 'thank God I waited', sometimes like today, it doesn't," Williams told Reuters, adding that she was proud of her efforts despite getting knocked out.

"That's just the way the cookie crumbles - sometimes you win, and sometimes you don't. That's just part of the sport of surfing," she said.