A young man who died in a national park after a car plunged into the water in the early hours of the morning has been identified. 

Emergency services were called to Audley Weir in the Royal National Park, south of Sydney, about 1.15am on Wednesday. 

Officers were told a blue Audi sedan and a silver Mercedes sedan had been driving down Audley Road, near Riverside Road, before the blue vehicle came off the road, entered the water and sank.

It's understood the driver, a man in his 20s, was able to free himself from the sinking vehicle and swim to safety. He was taken to hospital for mandatory testing.  

His passenger, also a man in his 20s, was trapped in the vehicle.

Police then recovered the body of a man about 10.20am.

He has been identified as 20-year-old Muhammad Kashif, a passionate cricketer from Casula who was studying electrical engineering. 

'Everybody will be remembering him because of his energy and smile,' former cricket coach Omar Khan told 9News on Wednesday night.

'We can't forget his smiley face.

'I won't be forgetting him for the rest of my life.'

The driver, and an 18-year-old man driving the Mercedes, underwent a roadside breath test, which returned a negative result.

'There was a passenger in the second vehicle, who is voluntarily at the police station providing police information about what happened,' Sergeant Steven Planinic said. 

The teenager has also been taken to hospital for testing.

It's believed there was no contact between the two vehicles.

The Audi was recovered from the water, with a crane lifting it from the weir on Wednesday morning.

Police established a crime scene and specialist officers have started an investigation into the incident.

'Charges may be pending for both drivers,' Planinic said. 

Motorists were told to avoid the area, with Audley Road closed in both directions through Wednesday morning.

A report will be prepared for the coroner.