A man’s body was recovered from the waters of Lake Del Valle south of Livermore on Saturday night — 51/2 hours after he jumped in the water to retrieve an oar off his family’s boat.

The man began to struggle immediately after jumping overboard, according to a statement by the East Bay Regional Park District’s public safety division. Minutes later, officers were summoned to the scene, and divers began to search for the man in a cove across the lake from the East Beach.

Police were flagged down by the man's family at 3:51 p.m. Saturday afternoon, park authorities said. At 9:21 p.m., divers from the Alameda County Sheriff Office’s dive unit located the man's body.

The man has not been publicly identified.