An island long believed to be in the middle of the Coral Sea, about 1,200 kilometres due east of the Queensland coast toward New Caledonia, exists on charts and maps but not in reality, Australian scientists say.

"Sandy Island" appears to be an error that has been propagated through numerous maps and charts, the Sydney Morning Herald reports.

Maria Seton, a geologist at the University of Sydney, was chief scientist on a 25-day voyage through the area that ended earlier this month. When she and her crew sailed past aboard the RV Southern Surveyor, they found nothing but blue sea — though the captain was exceedingly cautious.

"We became suspicious when the navigation charts used by the ship showed a depth of 1,400 metres in an area where our scientific maps and Google Earth showed the existence of a large island," Seton told the Herald. "Somehow this error has propagated through to the world coastline database from which a lot of maps are made."

The project gathered 197 different rock samples, geographical data from more than 6,800 kilometres of coast and mapped more than 14,000 square kilometres of the ocean floor.

"We all had a good giggle at Google as we sailed through the island," said Steven Micklethwaite of the University of Western Australia. "Then we started compiling information about the seafloor, which we will send to the relevant authorities so that we can change the world map."

The RV Southern Surveyor is Australia's Marine National Facility research vessel, the Herald reported.