A swimmer catches a wave at The Wedge wave break in Newport Beach, California, on August 27, 2014. Tall waves pounded the Southern California coast on Wednesday from Hurricane Marie in the Pacific Ocean, causing coastal flooding in Seal Beach, California, and forcing lifeguards to conduct rescues. Picture: Lucy Nicholson

Los Angeles - Waves up to six metres high crashed along the Southern California coast on Wednesday, as heavy and potentially dangerous surf from a Pacific cyclone drew crowds of surfers and spectators to Los Angeles-area beaches, officials said.

Large swells generated by Hurricane Marie began hitting the Southern California shore on Tuesday, causing coastal flooding in the Orange County town of Seal Beach after dark that inundated garages of 30 coastal homes.

Marie was downgraded on Wednesday to a tropical storm as it moved north off Mexico's Baja Peninsula, veering away from the West Coast but still causing extreme surf, National Weather Service weather specialist Stuart Ceto said.

Waves from the storm were the largest seen in Southern California since a pair of hurricanes swept through the Pacific within weeks of each other in 1997, he said.

At Will Rogers State Beach just south of Malibu, parking spots were filled as surfers scrambled out of their cars and paddled out into the ocean to brave the tall waves.

“If you don't know what you're doing, you can very easily get messed up very quickly,” said surfer Luis Abrishamian, 32.

Meteorologists said some of the biggest swells were hitting The Wedge, a popular body-boarding spot in Newport Beach that was seeing a steady onslaught of three-metre waves, with some breakers reaching as high as six metres.

Several thousand spectators gathered near The Wedge to watch the large waves, town spokeswoman Tara Finnegan said.

One body surfer who suffered a minor injury there on Wednesday had to be rescued by lifeguards in a boat, and inexperienced swimmers and surfers have been advised to stay out of the water, she said.

Los Angeles County lifeguards issued the same warnings and ordered curiosity seekers to stay off jetties and breakwaters. Farther north at Port Hueneme in Ventura County, waves crested at 4.5m, and breakers the same height were likely occurring along beaches elsewhere in Ventura and Los Angeles counties, Ceto said.

Large waves from Marie were likely to reach their peak on Wednesday, though the unusually large surf was expected to continue into Friday, he said.

The storm also disrupted ferry service between Los Angeles-area ports and the picturesque resort island of Santa Catalina, forcing the Catalina Express to cancel 10 departures on Wednesday after the island's main dock was closed due to high surf, ferry company executive Elaine Vaughan said. - Reuters