Three dead after light plane crashes into ocean

Three men, two of them teenagers, are dead after their light plane crashed into the ocean in front of onlookers at a popular fishing spot.

Police responded to reports of a plane crashing into the water at Long Bay near Murray Mouth, about 85km south of Adelaide, shortly before 4.30pm on Friday.

The pilot, a 57-year-old man from Morphett Vale, and his two passengers, aged 18 and 19, were found deceased.

Rough seas hampered efforts to retrieve the wreckage, with a police helicopter, firefighters, SES and private sea operators involved in the operation.

"The wreckage of that single-engine Cessna 210 aircraft has been brought into shore near the Murray Mouth," Senior Constable Rebecca Stokes told ABC Radio Adelaide.

"Tragic news for three families in South Australia today."

The Australian Transport Safety Bureau (ATSB) has commenced an investigation into the cause of the crash and is appealing for anyone with footage of the incident to come forward.

"Investigators will also interview witnesses and involved parties, collect available video footage and any recorded flight tracking data," the agency said in a statement.

A resident of nearby Goolwa told the ABC the scene near the crash was "chaos".

The crash site is a remote beach, but a popular fishing spot, where the Murray River meets the Southern Ocean.

Police will prepare a report for the coroner.

Meanwhile, floodwaters are hampering attempts to reach the scene of a light plane crash near Normanton in Queensland's Gulf Country.

Emergency services were called to the scene after the aircraft went down 800m west of Normanton airport about 8pm on Friday.

The pilot is believed to have been the only person on board but police and ambulance services were still trying to gain access to the crash site on Saturday.

The ATSB has been informed and will investigate the cause of the crash.