Three boats, a helicopter, and seven volunteer LandSAR teams were used to search an area from Manuka Island towards Balclutha for the man in his 60s.
Senior Constable Murray Hewitson said while a police dog team continued searching for the man last night after the main search was suspended for the evening, search and rescue personnel,
aided by additional police and local volunteers, searched a large tract of the Clutha River throughout the day.
"We have been well up the river, as far as Moore’s Beach, and will continue to search down to the mouth," Senior Sergeant Stan Leishman said.
"We are placing notices on all the public access ways along the river with a photo of Mr Marshall and contact details should anyone see him."
Mr Marshall, of the Otanomomo area 7km east of Balclutha, is in his 60s and has been missing since Thursday.
He is believed to be wearing dark green overalls and gumboots.
Anyone who has seen him, or who may have information about his whereabouts, is asked to call the police on (03) 363-7400.