From an aerial view just off the island of Mauritius, there is what appears be an underwater waterfall. The picture below illustrates this visual phenomenon:
The image can also be seen from the google maps satellite here.
What is responsible for this majestic illusion near the island? I have heard that it may be sand moving over the edge of an underwater cliff, and if so what causes the sand to be pushed off continuously without the process coming to a stop and what is responsible for this unique geographical landscape allowing this to occur?