Boy Bitten by 6-Foot Long Shark in First Attack of the Season at Florida Beach

A boy was seriously injured when he was attacked by a shark as he swam in chest-deep Florida waters, authorities said.

In what officials said was the first shark attack of the season at Neptune Beach, the 13-year-old boy and his stepfather were swimming when the child was bitten at about 3 p.m. Sunday.

The boy was pulled out of the water by bystanders as a lifeguard tower called in the incident, Neptune Beach police spokesman Michael Key told reporters.

Read: Shark Won't Let Go of Beachgoer Even as She's Taken to the Hospital

“All you see is just blood, dripping and dripping out for about 50 feet,” witness Lou Denmark told WJAX-TV.

Emergency responders rushed the teen to UF Health Jacksonville to be treated for an 8-inch bite behind his right knee and his calf, police said.

Read: Expert Gives Tips to Protect Yourself Against Shark Attack: 'Punch a Shark in the Snout, Grab His Gills'

His injuries were serious but not believed to be life-threatening, authorities said.

Police said that the size of bite indicates the shark is likely about 6-feet long.

Watch: Watch the Terrifying Moment a Man Got Knocked Off His Paddleboard By a Shark