The four-wheel-drive Nissan Patrol was stolen from Mannum at about midnight, and campers awoke to hear the car splashing into the water one-and-a-half hours later.

Joey Norris left his tent to see headlights slipping under the water but thought it was too dangerous to enter the river to check whether the car was occupied.

“There was no way I was going in to have a look to see,” he said.

Tailem Bend Country Fire Service crews attended shortly afterwards but heavy fog and the cover of darkness made it impossible to locate the car.

“As far as we knew, there was a car in there,” CFS captain Michael McEntee said.

“Whether there was a person in there or not, we were unsure.”

It was not until scuba divers from the South Australian Police Water Operations Unit arrived at the scene on Tuesday morning that it was confirmed the car was unoccupied.

It was retrieved from four metres of water, 25m from shore.

Police scuba diver brevet sergeant Glen McKenzie said the visibility under water was zero to half a metre.