A sea lion bit a woman swimming at San Francisco's Aquatic Park on Thursday in the fourth such attack in about a month. The woman apparently was not badly hurt, but authorities are worried about further attacks. A retired San Francisco firefighter also swimming in the bay around 7 a.m. helped the woman as she came out of the water, said Fire Department Lt. John Baxter, but the woman was able to walk on her own. She was taken to a hospital. Alice Ma said she and the victim are members of the South End Rowing Club, and that they were swimming together when the sea lion latched onto her friend and tried to drag her underwater. "It chomped down onto her," said Ma, who lives in San Jose. "It bit her and pulled." The woman didn't want to go to the hospital, "but we convinced her she needed to go," Ma said, adding that she "is very much an independent woman. She's a go-getter. She's a fighter." Lee Hammack, a member of the Dolphin Swim and Boat Club, was swimming nearby and saw the victim get out of the water. "She was bleeding pretty badly," he said. "But I know her - she's tough, she's not scared."