A group of friends, boating on the Hawkesbury River where a seaplane crashed into the water, have detailed the moments as it sank with six people on board.
A group of mates who witnessed a seaplane smash into the Hawkesbury River have revealed the terrifying moments they dived into the water to try and save the doomed passengers.
Todd Sellars, Lachlan Hewitt, Kurt Bratby and Will McGovern were boating on the river on New Year's Eve when the Sydney Seaplanes aircraft crashed into the water at Jerusalem Bay.
On board were experienced pilot Gareth Morgan, 44, high-profile UK businessman Richard Cousins, 58, his sons, Edward and William Cousins, aged 23 and 25, Mr Cousins' fiancee Emma Bowden, 48, and her daughter, Heather Bowden-Page, aged 11.
The group of mates rushed to the scene and dived in as the badly damaged plane began sinking, nose down, into the river.
Mr McGovern said the airplane's fuel was spilling out, hampering their efforts to reach the plane.
"The water was full of fuel, a massive slick across the top and the fumes actually burned your eyes," he told ABC.
"The boys were in the water diving down, trying to help these people inside the plane."
"I couldn't get the doors open because I kept running out of air," father-of-three Mr Sellars told Newscorp.
"I'm not sure if I saw a lady or it was the lights playing tricks on me.
"It was awful because we knew people were in there and we couldn't get them out."
The men attempted to tie the airplane's tail to their rubber dinghy to try and pull it to shore - but it was no use.
Mr Sellars said no one inside the cabin of the plane was knocking on the windows for help during it's final 13 metre descent to the riverbed.
All six occupants died in the crash and it took police divers hours to recover their bodies from the wreckage.
The seaplane remains on the bottom of the river with the Australian Transport Safety Bureau now working to refloat the aircraft, hopefully on Thursday.