Two drivers are currently in police custody.

A passenger of a car that crashed into a NSW weir has been confirmed dead.

The 20-year-old man was unable to get out of the car before it became submerged in the dark waters of Audley Weir in the Royal National Park south of Sydney about 1.15am on Wednesday.

Police divers retrieved the young passenger’s body and the car was pulled from the water about 10.20am.

The young passenger is yet to be formally identified, NSW Police said.

The driver, also a 20-year-old man, was able to free himself from the sinking blue Audi and get to safety.

It is unclear at this stage how long it took for the car to become fully submerged.

But NSW Police acting inspector Steven Planinic said two cars were involved in the incident.

The Audi crashed into a silver Mercedes, allegedly driven by an 18-year-old man, before it entered the water, NSW Police allege.

Both drivers are currently in custody, being interviewed by police at Sutherland Police Station.

A passenger of the Mercedes is “voluntarily at the police station providing police information about what happened,” Planinic said.

Police are looking into whether the two cars were racing but have not yet confirmed how the crash occurred.

Roadside blood alcohol testing returned negative results, before the drivers were to the hospital for mandatory blood testing.

No charges have been laid at this stage.

Planinic said the circumstances were “tragic” and described “difficult conditions for crews as well”.

Investigations, including a mechanical examination of the Audi, are ongoing.