An island off the South Pacific has been discovered to be a hoax or non-existent by a group of Australian scientists, despite being visible on marine charts and world maps, even on Google Earth.

The land mass, named Sandy Island, was supposedly located between Australia and New Caledonia. It is identified as Sable Island by the Times Atlas of the World.

But when scientists from the University of Sydney, aboard Southern Surveyor, a new Marine National Facility research vessel, went looking for the island to confirm its existence, it found only a massive 1,400 metres or 4,620 feet of blue deep ocean waters.

The scientists were puzzled with the discovery.

"Even onboard the ship, the weather maps the captain used had showed an island in this location," Dr Maria Seton, the voyage's chief scientist, said.

For at least a decade, the non-existent island has been featured in a number of publications relative to geography and marine subjects.

"We wanted to check it out because the navigation charts on board the ship showed a water depth of 1,400m in that area - very deep," Dr Seton told the AFP after a 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."

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

But according to some forums, such as www.abovetopsecret.com, the questionable existence of the island was deliberately placed on the map.

"Many mapmakers put in deliberate but unobtrusive and non-obvious 'mistakes' into their maps so that they can know when somebody steals the map data," an unidentified commenter was quoted by ABC News.

A Google Earth spokesman said they refer to a diversity of authoritative sources when creating their maps.

"The world is a constantly changing place," the spokesman told AFP, "and keeping on top of these changes is a never-ending endeavor."