A 30-year-old man who deliberately drove his car into Perth's Swan River is in intensive care in hospital, police say.

They have not yet named the man, from Yokine in the city's inner northern suburbs, and are attempting to notify his family, who live overseas.

He was taken to Royal Perth Hospital in a critical condition after being pulled from the water by police officers on Sunday.

The man was seen driving his white Hyundai sedan along a footpath to the edge of the water at Barrack Street jetty at about 10.30am WST.

After stopping the vehicle and placing down some personal items including an empty jerry can, he got back into his car, accelerated hard and ploughed through a temporary fence.

The car hit rocks at the water's edge, catapulting the vehicle metres into the river.

Witnesses reported seeing the driver treading water as the car sank, before swimming back under the waves and into the car.

He was submerged inside the car for some minutes before police arrived, dived in and rescued him.

They resuscitated the man before ambulance officers arrived and continued efforts to revive him.

Police said the incident was highly unusual.