SAN MATEO (Map, News) - The life of a 20-year-old man who took an ill-advised dip in the Bay wearing just his Speedos was saved Sunday night by a resourceful park ranger and a volunteer Coast Guard member.

The unidentified man was on the beach at Coyote Point in San Mateo with his brother and a companion Sunday evening when he decided to go for a swim, said Park Ranger Rick Munds, who was on duty at the time.

Caution set in and the police were called, however, when the man’s body was bobbing more than 100 yards from shore shortly afterward, Munds said. A member of the Coast Guard Auxiliary, a volunteer force that patrols the water’s edge, Munds contacted the U.S. Coast Guard.

But despite the Coast Guard’s immediate efforts to dispatch a 25-foot boat from Station San Francisco at Yerba Buena Island, spokeswoman Lt. jg Lauren Kolumbic said, it still had 15 miles to go before arriving at the beach.

Minutes passed as Munds and authorities watched the figure float farther away in the falling dusk. Finally, Munds took matters into his own hands. He hauled a San Mateo County Parks skiff, and with two members of the Foster City Fire Department, directed the boat about 400 yards out, where the figure had last been seen, Munds said. It took a few minutes to find the swimmer, who wasn’t clearly visible in the falling darkness, but they finally spotted him.

“He was so cold he couldn’t answer questions. We asked him what day it was and he said he didn’t know,” Munds said.

At 7:48 p.m., the Coast Guard boat arrived and the man was taken ashore, where he was then taken to the Mills Health Center. The man has since been reported to be conscious and in stable condition, Kolumbic said.

It’s still a mystery why the man decided to go into the water, Munds said.

“His brother said they grew up swimming in the Bay,” Munds said. “Who knows how he stayed conscious for that long.”

kworth@examiner.com