Sandy Island, also known as Sable Island, is located between Australia and the French-controlled island of New Caledonia in the Coral Sea. It's depicted as being about 15 miles (24 kilometers) long and 45 square miles (117 square kilometers) in area, which makes it about one-and-a-half times the size of Manhattan [source: Krulwich].
Or at least that's what numerous maps — from a 1908 chart to Google Maps — have depicted over the years. The problem, though, is that when University of Sydney researchers sailed a ship into the area to visit Sandy Island in 2012, they didn't find anything except ocean.
"It's on Google Earth and other maps so we went to check and there was no island. We're really puzzled," one of the scientists, Dr. Maria Seton, explained in a 2012 BBC interview.
What's even odder, though, is that some people had reported seeing Sandy Island, though not recently. Back in 1772, British explorer James Cook passed close to it, and sailors on the British ship Velocity apparently saw it when they sailed by in 1876. But nobody ever actually set foot on it.
Now those accounts seem a bit fishy. The Australian researchers decided to visit the island because sonar maps of the sea floor showed very deep water where Sandy was supposed to be. As geologists, they wondered how a land mass could be floating on the surface, with no substructure or seamount beneath it. It just didn't seem plausible. And as it turns out, it wasn't [source: Krulwich].
Google Maps now describes Sandy Island as "nonexistent" but still provides a ground-level view of a sandy beach.