Even experienced surfers stayed out of the waves that pounded north- and west-facing shores of O'ahu yesterday for the second day in a row.

The waves, while not as large yesterday as Sunday's 25- to 35-foot surf, were just as gnarly and unsafe for beachgoers and swimmers, said Jim Howe, Ocean Safety operation chief.

The National Weather Service said the surf yesterday was 20 to 25 feet on north-facing shores and 15 to 20 feet along west-facing shores of Ni'ihau, Kaua'i, O'ahu and Moloka'i.

The weather service last night canceled a high surf warning and replaced it with a less-severe high surf advisory. Surf today is forecast to be 12 to 15 feet along north-facing shores, eight to 10 feet along east shores and six to 10 feet along west shores.

The giant surf also canceled the Quiksilver Big Wave Invitational in Memory of Eddie Aikau surf competition yesterday. The event has only been held seven times in the past 23 years because it requires that open-ocean swells reach a minimum of 20 feet, or a wave face of more than 30 feet. The last event was in 2004, when waves in Waimea Bay reached 30 to 50 feet. The contest invites only 24 big-wave riders to participate in two rounds of competition.

On Sunday, the conditions were too rough for the world's big-wave riders, said Jodi Wilmott, spokeswoman for the group putting on the event.

"My advice is to stay out of the water," Wilmott said. "This kind of surf is for accomplished surfers only, the top; less than 1 percent of the surfers can get a go at it. And today it's bad conditions, too. Not as huge as Sunday; the waves are shredded."

Reach Suzanne Roig at sroig@honoluluadvertiser.com.