There are grave concerns for a man who is missing after a car rolled down a boat ramp, struck a woman, and entered the water off Sydney’s lower north shore.

Emergency services were called to reports that a car had accelerated through a car park, hit a woman, and crashed through a fence before plunging into the Parramatta River near the boat ramp at Manns Point in Greenwich about 4.20pm.

When firefighters arrived, paramedics and police were already on the scene, treating a woman who had also been in the water.

Two nearby swimmers had dived into the water to help the woman.

She was treated by paramedics for lower leg injuries and taken to Royal North Shore Hospital with a suspected broken ankle, bruises, abrasions and shock.

“There is no visibility of the car that is in the harbour,” FRNSW Superintendent Adam Dewberry said.

The car is believed to be up to 10 metres underwater.

Dewberry said there were grave concerns for the missing man.

“We can’t find the car at the moment because it is so deep, and the information we have is that it has floated off the waves,” he said.

“It was taking on water quickly.”

Police divers will explore the bottom of the harbour for the vehicle.

With light fading quickly, Dewberry said the car would likely be recovered tomorrow.