thumbnail Getting to the bottom of the underwater waterfall
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Getting to the bottom of the underwater waterfall © Hemis/AlamyJoin Our GIFs Group
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 currents over the edge of an ocean shelf. But we"re probably not alone in thinking at first glance that the ocean is pouring into some massive unseen drainpipe.