The island that isn't there!
Or maybe it's the island of Doctor Moreau...
Sandy Island looks like a gaping hole in the Coral Sea. About 16 miles long, north to south, it could make the perfect beach nirvana. But the University of Sydney scientists found only ocean 4,620 feet deep when they went to the site while on a research expedition. The depth would preclude the island sinking.
Read the "More Info" linky for the whole story of this non-place.