"We got there and it was what appeared to be a body," said Bernard Peters, county fire supervisor.
"We have no idea who this is. We are waiting for homicide (detectives) and the coroner's office to arrive, said county sheriff Sgt. Rich Nagler.
The person was pronounced dead at the scene but not identified, the Los Angeles Times reported.
A search of the area has been on since Friday for Bryce Laspisa, 19, whose pickup truck was found overturned near the lake.