Getting to the bottom of the underwater waterfall

From this vantage point high over the Indian Ocean, we have a spectacular view of the 'underwater waterfall' formed off the coast of Mauritius. Not a true waterfall, this is an optical illusion - it's really the trails of sand and silt deposits on the seafloor being washed by ocean currents through an opening between coral reefs. But we're probably not alone in thinking at first glance that the ocean is pouring into some massive unseen drainpipe.
© Hemis/Alamy