A SEA plane has crashed into the Hawkesbury River north of Sydney killing six people - four of them are reported to be British.
The plane was discovered upside down at the bottom of Corwan Creek under 13 metres of water.
A police spokesperson has said: “'For reason that are not known at this stage, the plane has hit the water and it has subsequently sunk.
“At the time of the collision, there was a pilot and five passengers on board. I can confirm the six people on the plane are deceased.'
Local reports say four of the passengers were British and an 11-year-old boy was among the dead.
The plane was believed to have been travelling from the Cottage Point Inn to Rose Bay.
TV journalist for 7NewsSydney, Freya Cole, tweeted: "Horrific details coming out of this seaplane crash in the Hawkesbury River.
"Among the six victims are believed to be an 11 year old boy, the pilot and 4 British nationals."
The crash took place at 3:10pm local time.
Debris and oil were found on the surface of the sea where the plane went down.
Rescue vessels, including police and ambulance helicopters, attended the scene.
The journey from Cottage Point to Rose Bay would normally take 20 minutes.
The Australian Transport Safety Bureau will investigate the incident.