A South Pacific island identified on Google Earth and world maps does not exist, according to Australian scientists, who went searching for the mystery landmass during a geological expedition.

The sizeable phantom island in the Coral Sea is shown as Sandy Island on Google Earth and Google maps, supposedly midway between Australia and the French-governed New Caledonia.

The Times Atlas of the World appears to identify it as Sable Island and according to Dr Maria Seton, the weather maps used by the Southern Surveyor, an Australian maritime research vessel, also say it is there.

But when the Southern Surveyor, which was tasked with identifying fragments of the Australian continental crust submerged in the Coral Sea, travelled to where the island was supposed to be, it was nowhere to be found.

"We wanted to check it out because the navigation charts on board the ship showed a water depth of 1,400 metres in that area - very deep," Dr Seton, from the University of Sydney, said after the 25-day voyage.

"It's on Google Earth and other maps so we went to check and there was no island. We're really puzzled. It's quite bizarre.

"How did it find its way onto the maps? We just don't know but we plan to follow up and find out."

News of the invisible island sparked debate on social media, with Charlie Loyd pointing out on Twitter that Sandy Island is also on Yahoo Maps as well as Bing Maps "but it disappears up close".

Google said it always welcomed feedback on a map and "continuously explores ways to integrate new information from our users and authoritative partners into Google Maps".

"We work with a wide variety of authoritative public and commercial data sources to provide our users with the richest, most up-to-date maps possible," a Google spokesman said.

"One of the exciting things about maps and geography is that the world is a constantly changing place, and keeping on top of these changes is a never-ending endeavour."

The Australian Navy's Hydrographic Service - the department responsible for producing official nautical charts - told Fairfax media it took the world coastline database "with a pinch of salt" since some entries were old or erroneous.

AFP