WAIMEA — A huge winter swell turned much of the North Shore into white, frothy soup yesterday. But at certain spots, the ocean offered up heaving turquoise to the delight of big-wave surfers and the crowds they attract.

The swell yesterday was forecast to produce waves of 25 feet to 35 feet at its peak for north- and west-facing shores of O'ahu, Kaua'i and Moloka'i, prompting a high-surf warning through 4 p.m. today from the National Weather Service. Although it is expected to diminish today, another large west-northwest swell is expected Christmas night through Monday.

Beaches along the North Shore were closed to swimming and walking along the water's edge. And Waimea Bay, at least in the morning, was the only spot offering ridable waves. By the afternoon, lifeguards were calling Waimea "ugly."

Still, as it often is on a big day, Waimea Bay was the broad-shouldered star attraction when the surf was good.

Crowds lined the highway to catch the action in the morning. The surf was not always as clean as some would like, but it kept rising, and by noon, some 20-foot sets swept toward shore.

"It's beautiful," said Fabiana Atwood, a 37-year-old Hale'iwa resident who watched surfers at the bay. "It's breathtaking to watch. I cannot imagine being a surfer."

Lee Buckland, a 30-year-old surfer visiting from England, called the waves at Waimea Bay "fantastic," but "too challenging for me." Even as he spoke, two surfers dropped into a 15-footer and streaked across its face in a speeding attempt to outrace a mountain of whitewater.

And they did.

"I reckon it's everyone's dream to surf a wave that size," Buckland said. "But it's easy to sit on the beach and watch. Being a surfer out there is a whole different experience."

Micky Hooks was out there for several hours. He would wait 40 minutes between decent, ridable waves, battered by the wind, but it was worth it, he said.

"It's a fun day," Hooks said. "I got a couple that were solid."

How big?

"I'm not sure how big it was," he said with a broad smile that said even more. "I was just trying to make it."

Jamilah Star said the waves were not the biggest she had ever been in, but the wipeouts were among the worst she had ever endured. The experience left her with a grinning, adrenaline buzz.

"Today was super-gnarly," Star said.

The wind and waves would conspire to unexpectedly pitch a surfer forward, sometimes more than once on a single wave, she said.

"You would air-drop with the wind in your face and when you landed and thought it was a normal wave, it would keep pitching you forward," Star said.

Just around the bend, a little south of Waimea Bay at Three Tables, O'ahu Civil Defense volunteer Dan Murdock, a 74-year-old retiree from Kahuku, strung a new line of red safety tape 20 yards closer to the highway.

Tourists were eager to get close to the water until he explained the need for a safe buffer.

"Most are tourists and they are fine with it when you tell them the surf is on its way up and 30 feet will get 'em, suck 'em right out," Murdock said.

North Shore lifeguards were busy keeping people back, said Capt. Bodo Van Der Leeden. He said many surf spots "were closed by nature," and even the experts scoffed at going out.

"A couple of surfers in some areas were trying to give lifeguards some lip, but they really had no clue as to what they were getting into," Van Der Leeden said. "It just goes to show you that if the lifeguards weren't there, people would be going out into disaster."

Reach Mike Gordon at mgordon@honoluluadvertiser.com.