HUNTINGTON BEACH (CBSLA.com)  — The Coast Guard has joined the search for a missing 18-year-old swimmer.

The teen, identified as Shaun Linn, was last seen swimming near Bolsa Chica State Beach, near Huntington Beach, about 50-100 yards off shore.

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The Coast Guard’s Los Angeles-Long Beach sector received a call from a Good Samaritan around 5:20 p.m., reporting that Linn entered the water and did not return to the surface.

The Coast Guard immediately launched a MH-65 Dolphin helicopter crew from Point Mugu and a 45-foot boat from Station Los Angeles to search for the  missing swimmer.

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Bolsa Chica State Park Lifeguards, Huntington Beach Harbor Patrol and a helicopter from Orange County Sheriff’s Department are also assisting in the search.

Linn was reported to be last seen wearing red and white trunks.

He was with two other swimmers who were rescued. One of them was taken to the hospital in unknown condition.

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If anyone has any information regarding Linn, please contact Coast Guard Sector Los Angeles-Long Beach command center at (310) 521-3801.