The victim had been training with 20 to 25 other 11- and 12-year-old kids at the time of the accident. They had been practicing a speed drop, which is when the lifeguard drops off the boat to reach a swimmer in distress.
"Apparently, the 11-year-old girl was away from the group," said Jim Amormino from the Orange County Sheriff's Department.
Officials said the boat was driven by a 53-year-old Marine safety officer, who has more than 30 years of experience.
"The conditions were choppy, and I'm sure the operator of that boat, who is very, very experienced, did not see the young girl," Amormino said.
Initially, a city spokesperson said the victim had been injured by the boat's propeller, but authorities now say they are not sure what caused the severe cuts to her lower body.
This is the first accident between a junior lifeguard and a lifeguard boat.
Junior lifeguard program is an eight-week program that has been around since 1964. It was in its fifth week on Tuesday.