The famous "underwater waterfall" off the coast of Mauritius is not an actual waterfall but an optical illusion caused by sand and silt deposits flowing down an underwater slope.

Location: The most well-known example is located near Le Morne Brabant, a UNESCO World Heritage Site, on the southwest coast of Mauritius in the Indian Ocean.

Visible from above: The underwater waterfall illusion is best viewed from a helicopter or aerial perspective, making it a popular attraction for tourists and photographers

Turbid water movement: The way the water moves and refracts light as it flows down the slope also plays a part in making the sand look like it's cascading downward like a waterfall.

Steep underwater drop: While the illusion is due to sand movement, there is actually a steep underwater cliff.

Geological significance: This phenomenon occurs due to a unique geological formation called a submarine plateau, which ends in a steep drop-off that causes the sediment to flow downward.

Marine life thrives around it: Despite the dramatic appearance, the area is home to vibrant marine ecosystems, with coral reefs and abundant sea life thriving around the underwater cliffs.

Not the only one: While the Mauritius underwater waterfall is the most famous, similar phenomena can be observed in other locations around the world, particularly where sand or silt flows off steep underwater slopes

Here are 10 surprising facts about underwater waterfalls: