POLK COUNTY, Fla. (WFLA) — Polk County authorities are desperately searching for a 9-year-old boy who fell off his father’s pontoon boat Saturday, and disappeared into the murky water.

According to the Polk County Sheriff’s Office, the incident took place at Lake Annie, south of Dundee. Deputies said the 9-year-old Port St. Lucie boy and his two brothers were on their father’s pontoon boat when he fell over the front and was struck by the boat’s propeller.

The father leaped into the water to look for his son while another child called 911.

Deputies said the 9-year-old was not wearing a personal flotation device when he fell into the water. Florida law does not require the child to wear a life jacket.

First responders arrived at the Lake around 2:40 p.m. and immediately launched boats in an effort to look for the boy.

PCSO’s Marine Unit, Underwater Search and Recovery Team (USART), Aviation Unit, and Drone Units were all utilized in the ongoing search effort.

“It’s a tragedy, and an unimaginable nightmare for the family of the boy,” Polk County Sheriff Grady Judd said. “We are using extensive resources to find him. We’re working in a large lake with depths up to about 16 feet, with poor visibility, but we’ve been out there 24 hours a day, and will continue to be there until we find him.”

The search for the child remains ongoing.