“The underwater waterfall “ illusion at Mauritius Island is an island nation in the Indian ocean around 2000 km off the southeast coast of the African continent. When viewed from above a runoff of sand and silt deposits creates the impression of an “ underwater waterfall”. Whatever you are witnessing is actually sand from the shores of Mauritius being driven via ocean currents off that high, coastal shelf, and down into the darker ocean depths off the southern tip of the island.