A good Samaritan dived into the cold waters off Pier 1 on Thursday morning in an effort to save a woman he saw floating face down in the water.

Fifty-one-year-old Anthony Deluz was clutching a piling and trying to hold the 21-year-old woman’s head above water when Coast Guard rescuers arrived at 8:37 a.m., Coast Guard spokeswoman Lt. Amy Marrs said.

The young woman jumped into the water before 8:30 a.m., San Francisco Fire Department Lt. Al Posey said.

Officials say it may have been an attempted suicide.

Three minutes later, Deluz and the 21-year-old woman were both brought aboard a 25-foot Coast Guard rescue boat. They were checked for signs of hypothermia and in stable condition at a local hospital early Thursday afternoon, Marrs said.

Hypothermia in Bay waters — where the temperature is around 55 degrees — typically doesn’t set in before an hour, Posey said. Pier 1 is next to the San Francisco Ferry Building, across from Justin Herman Plaza.

mcarroll@examiner.com