A police officer dragged an unconscious man from his submerged car after it plunged off the Barrack Street jetty into the murky Swan River yesterday.
The man was in a critical condition in Royal Perth Hospital last night.
Police and emergency service workers were commended for their quick actions after the dramatic rescue, which happened in front of dozens of bystanders about 10.45am.
Insp. Derek Staats said there was zero visibility in the water when one officer dived down to the car, which was submerged in up to 4m of water, to check whether anyone was trapped.
The officer felt through the passenger window before swimming to the driver's side, where he touched a person through the open window and pulled him out.
Two other officers who had swum to the sunken car and a State Emergency Service volunteer helped bring the unconscious man to the jetty, where other officers and paramedics tried to revive him.
Police were not sure why the man's car plunged into the river but emergency services were called to the waterfront after witnesses reported seeing the car accelerate off the western end of the jetty.
Insp. Staats said the first police officers to arrive had acted quickly after witnesses told them a man was in the water.
"Their actions are admirable," he said.
Witnesses told police they saw a man driving along a jetty footpath before stopping near the water and leaving some personal items and an empty fuel container on the water's edge.
"One witness . . . observed the car driving along the footpath towards the jetty . . . and a few minutes later he heard the revving of the car and squealing tyres and when he looked up, he saw the car driving off the end of the jetty," Insp. Staats said.
Witnesses told police they saw the man they believed was the driver treading water on the surface as the car sank before he went under.
They told police the man had been in the water "some minutes" before they arrived.
Farhad Mobarra, who saw the rescue, said he saw bubbles in the water before police officers dragged the man to the surface. "I just started shaking . . . it was a very difficult time to see a fainted body come out of the water," he said.
Witness Margie Bradley said it appeared police, as well as fire crews and paramedics, had responded very quickly. Divers made sure no one was trapped inside the car.
The incident happened just metres from the Aquatic Super Series open water swimming event.People seeking support or information about suicide prevention can phone Lifeline on 13 11 14.