Mr Marshall’s body was found in the Clutha River by members of the police dive squad.
Sergeant Jason Leadley said "while this was an outcome no-one wanted we would like to acknowledge the Search and Rescue volunteers from across the district who have assisted with the search over the last three days."
Mr Marshall, of the Otanomomo area 7km east of Balclutha, was aged in his 60s and had been missing since Thursday.
Three boats, a helicopter, and seven volunteer LandSAR teams were involved in the extensive search operation.
Sgt Leadley offered sympathies to the friends and family of Mr Marshall.
The death will be referred to the coroner.