LOS ANGELES (CBSLA.com) — High surf, rip currents and minor coastal flooding continued Thursday for a third straight day due to huge swells from Tropical Storm Marie off the coast of Mexico, the National Weather Service said.

South-facing beaches were most affected, according to the NWS, which said the high surf is “the most significant southerly swell event since July 25, 1996.”

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The biggest surf hit beaches in L.A. and Ventura counties, with waves averaging 10 to 15 feet and isolated sets reaching 20 feet Thursday evening.

Lifeguards rescued a 27-year-old swimmer Thursday night in Venice Beach near the 2100 block of South Ocean Front Walk. The man was transported to a hospital in grave condition.

Those who attempt to surf or bodyboard were warned that a high surf advisory remains in effect until 6 p.m. Friday in L.A. and Ventura counties and 1 p.m. Friday in Orange County.

In Seal Beach, an 8-foot sand berm that was erected Wednesday prevented coastal homes from flooding overnight.

“I feel a lot safer with that up. I don’t have to worry as much,” one resident said.

On Wednesday, water from high tide left three feet of standing water along the boardwalk and officials were also forced to partially close the pier due to safety concerns.

Further north, Malibu Pier will remain closed through Friday due to damage the 109-year-old structure sustained from the waves.

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In Point Mugu, the Cove House collapsed into the ocean around 10 p.m. Wednesday after its pilings took a beating from the surf.

For many, the guard house near Sycamore Canyon served as a spot that lifeguards referred to as home for 40 years.

Norm Chapman, a retired lifeguard, said he worked out of the Cove House every day since 1980.

“A lot of lifeguards have put a lot of time into it over the years; it’s sad,” Chapman said. “It’s hard not to get choked up; I’ve been here 35 years.”

According to authorities, more than 250 people have been rescued by lifeguards since Tuesday.

Conditions will remain dangerous for swimmers through the weekend.

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