The incident happened about noon while the woman was inner tubing in the Intracoastal with friends near Bayshore Drive, said Chantel Botting, division chief for Fort Lauderdale Fire-Rescue.
She was identified as Jessica Vaughn.
Broward Health Medical Center officials said the woman was undergoing surgery late Sunday afternoon, according to The Associated Press.
Vaughn’s friend, Kyle Branston, told CBS4 that he was on an inner tube next to her around 1:30 p.m.
“All the sudden she said something bit her or cut her, and I first thought she was joking,” Branston said. “She didn’t want to get into the water to begin with because she said the water was dark and she couldn’t see what was in it.”
Branston said he first thought Vaughn had been cut by glass, but a half-moon wound on her leg was an apparent shark bite. Vaughn also told her friends she saw the shark.
“When the shark bit her down low, I guess the fin came up and hit her in the head,” said Nick Russo, who was also tubing with the group.
Friends wrapped her leg to stop the bleeding and rushed her to the nearest dock on Bayshore Drive.