The Livingston County Sheriff's Department's dive team is searching for the body of a woman who is believed to have drowned in Lake Shannon near Fenton.
Fire officials say the 20-year-old jumped into the water from a boat and failed to resurface. Her name has not been released.
Officials say they are treating the situation as a recovery, not a rescue operation.
The water where the woman jumped in is between 15 and 20 feet deep.