A 20-year-old man who died after becoming trapped in a sinking car that had swerved into the water in Sydney's Royal National Park has been identified as a university student and budding cricketer.

The car is believed to have veered off the road before crashing into Audley Weir in the Sutherland Shire about 1.15am.

The 20-year-old driver of the blue Audi was able to free himself from the sinking car and was taken to hospital for mandatory testing.

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He has since been released and was in custody at Sutherland Police Station.

The passenger became trapped in the vehicle, and his body was found, along with the submerged car, following a multi-agency search.

He has been identified as 20-year-old Muhammad Kashif, a university student studying electrical engineering and a budding cricketer from Casula.

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

"We can't forget his smiley face.

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

Sergeant Steven Planinic said the 18-year-old driver of a second vehicle, a silver Mercedes, was speaking with police and the car had been seized.

"There was a passenger in the second vehicle, who is voluntarily at the police station providing police information about what happened," he said.

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Police say there does not appear to have been any contact between the two vehicles.

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

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