San Francisco » A boat capsized in the San Francisco Bay sending five adults and three children, including two in critical condition, to a hospital, officials said.

The boat carrying 27 adults and three children capsized for unknown reasons Saturday afternoon about 100 yards off Pier 45, said San Francisco Police Officer Giselle Talkoff.

One 5-year-old boy, who was unconscious and not breathing when he was pulled out of the water, was eventually revived and expected to make a full recovery, according to Jonathan Baxter, a public info officer for San Francisco Fire Department. Another 5-year-old boy was also initially listed in critical condition but was later downgraded to stable, he added.

All eight people who were hospitalized were expected to survive, Baxter said.

Photographs posted on social media showed youths and adults barefoot and wrapped in thick gray blankets on shore after being rescued. The boat was fully submerged in the water.

Fisherman David Griffiths told the San Francisco Chronicle he tossed life jackets to the people in the water. He was taking off his shoes and getting ready to jump in when the first rescue teams arrived, Griffiths said.

Fire Department Assistant Chief Bob Postel said rescue teams from the fire and police departments and the U.S. Coast Guard all rushed to the scene.

“There were lots of rescue boats on the water because of Fleet Week, so we were fortunate,” he said. “We were able to get everybody out and accounted for quickly.”

A good Samaritan performed CPR on the boy who wasn’t breathing until a police officer was able to take over, Talkoff said.

Griffiths said it was jarring to see the boat upend during what had been an otherwise beautiful day on the water.

“Seeing the bottom of it, that’s not a normal thing,” he said.

Authorities were investigating the cause of the accident.