A robotic device has helped locate the body of a man who drowned at a popular northern NSW water hole.

Police say at 2:15pm on Thursday a 30-year-old man went swimming in a lagoon at Dalwood Falls at Alstonville, near Lismore.

They were told the man jumped from a tree into the water but never resurfaced.

Police, NSW Fire and Rescue and paramedics searched the area and the man's submerged body was found with the help of the device several hours later.

AAP