HALF MOON BAY. Calif. -- As 30-to-40-foot mountains of moving water charged across the North Pacific on Friday, big-wave surfer Ion Banner was trying to think about something -- anything -- else.

"Sometimes you get too excited about it, so over the years I've tried to learn not to think about it," the rangy, 38-year-old Banner said in a recent interview at his small house on a hill overlooking Pillar Point Harbor. Just beyond the rocky seawall that shields the boats from the open ocean is one of the surfing world's most awesome spectacles, the nasty and unpredictable break known as Mavericks.

On Saturday, Banner will be among two dozen elite big wave surfers who will point their big-wave "gun" surfboards down the three-story faces of these waves in the latest installment of the legendary Mavericks Surf Contest. Banner has competed several times before, with his best showing -- a 10th-place finish -- coming in 1999.

As the only Half Moon Bay resident in this year's field, Banner earned his spot in the lineup through years of braving the region's frigid, fog-enshrouded waves with little or no company, unlike most of the others who trot the globe on the professional surfing circuit.

But even though Banner may know Mavericks well, there's little home-field advantage, even after 15 years of surfing the infamous break.

"The challenge of a wave like that never goes away," said Banner. "It's just too intense."

Each winter, when huge, storm-generated swells batter the Northern California coast, the world's top big-wave riders are put on notice. Within a four-month window that typically begins in early December, contest organizers wait for ideal conditions before giving invitees little more than 24 hours to travel from wherever they are in the world to Half Moon Bay, about 20 miles south of San Francisco.

This year's call went out late Thursday. Banner was on his way to Oregon to compete in a tow-in surfing contest when his phone rang near Eureka, Calif. He turned the car around and started back.

"I've been trying to relax all day," he said Friday. "My heart's been pumping all morning."

Contest organizer Jeff Clark had been watching the weather all week, and saw his opportunity on Thursday to get this year's contest going.

"With this storm lining up, coming at us from the International Dateline unobstructed, I wasn't going to let this one go by," said Clark, the surf pioneer who "discovered" Mavericks in 1975 and for about 15 years was the only one to surf it.

A big day at Mavericks requires a certain combination of meteorological events.

That began to play out Monday, when a storm with strong winds developed in the North Pacific, south of the Aleutian Islands. As it bulldozed across the ocean's surface, it generated a chain of moving swells that began traveling toward Mavericks, marching in procession across thousands of miles of open ocean like the concentric ripples created when a stone is tossed into a pond.

"It's a freak of nature for these multiple things to come into play simultaneously," said Mark Sponsler of Stormsurf.com, the forecasting service that helps organizers decided when to call the contest.

Some winters, including last year, it never happens within the window of time set aside for the contest. Saturday's will be the sixth contest since the Mavericks event was born in 1999.

The swells travel for five days before reaching the shallow waters of the Mavericks reef, about 11/2 miles off Pillar Point.

What makes this break special is a small section of reef that juts out into deep water like a finger. This sudden change in depth forces the moving mass of water to heave upward as it rolls over the reef.

Then gravity brings it crashing back down again.

The wave is so steep that Mavericks surfers and their boards often lose contact with the surface and free-fall down the face before hitting the water at extraordinarily high speeds as they try to outrun the powerful flood of churning whitewater on their heels.

If surfers lose their balance, they can be held underwater for what can seem like an eternity, pinned to the jagged reef, or pin-balled through the craggy rocks between the reef and the beach.

These treacherous conditions are precisely why Mavericks was considered too dangerous to surf for decades.

In the 1980s, as a teenager, Banner would walk with his dog along the reef at low tide. Clark shaped his first Mavericks board, and Banner says he was among the first wave of surfers who followed Clark's lead in 1989. Even then, it was still a small, local crew.

Today, when Mavericks breaks, local surfers are joined by a much larger group, including some of the world's elite big wave riders. But the wave's size and the skill required to surf it keep the cherished break from getting too crowded.

"Mavericks is one of those places that will take care of itself," said Clark. "No one owns Mavericks, the best in the world have come here and surfed it. But as soon as they think they got it they're being held down for 20 seconds."

And the contest has become a lucrative event broadcast on network television and featured in magazines and newspapers. The winner wins $75,000.

Banner is happy to see Half Moon Bay -- a town otherwise best known for its annual pumpkin festival -- get some recognition from the international surfing community. But the contest has also created some problems for locals.

"It's definitely a mixed bag," he said. "It's affected our area positively as far as small businesses and bringing attention to the area. But from a local standpoint, the area has gotten kind of exploited."

When the window for Mavericks opened on Dec. 7, Banner's life became a bit more complicated. He started constantly checking his cell phone for the call announcing the contest. He was afraid to stray too far from home and be unable to get back in time.

"For a lot of the pros, they're flying around anyway so it's no big deal to them," he said. "Their sponsors are flying them here.

"I can't go other places and pay to fly back," he said. "So I'm pretty much just waiting for it.

When not surfing, Banner makes ends meet working construction and odd jobs. He does have a few sponsors who give him wetsuits and leashes, but no salary.

The training never ends, but it's not exactly a hardship. Most mornings, Banner is up at 5:30 a.m. He walks past his snoring pit bull and pulls his shortwave weather radio from a kitchen shelf. If the staccato, computerized voice from the National Weather Service gives favorable news on the swell, he goes surfing.

At 38, Banner figures he's got at least 10 years of big-wave surfing left if he keeps himself in good shape.

"I'm more limited with the age," he said. "I have to give myself a chance to recuperate which I didn't when I was younger."

Banner sees his chance to ride alongside some of the world's best watermen as the result of a lifetime of hard work and dedication.

"I don't surf a lot of contests," he said, "so it gives me a big rush. It's hard to sleep."