The worlds largest waterfall is located under the sea.

The title of the world's largest and tallest waterfall belongs to the Denmark Strait Falls, which is 3,500 meters high. This waterfall is a sheer drop in the strait between Greenland and Iceland, meaning it is underwater.

Temperature and salinity differences power most ocean currents, so the Denmark Strait waterfall has a flow rate of nearly 3.5 million cubic meters per second.

The Denmark Strait crosses the Arctic Circle and acts as a funnel for polar waters to flow from the Nordic seas into the Atlantic Ocean.

The waterfall is caused by the density difference between the waters of the Greenland Sea and the Irminger Sea. North of the Denmark Strait, the surface water is exposed to cold Arctic air and becomes colder as some of the water freezes. Salt then concentrates in the unfrozen area. The cold, salty water is denser than the warmer water, so it sinks to the bottom, while the lighter layer rises to the top. This causes a deep current to flow south through the strait, emptying into the Irminger Sea in the North Atlantic.

The Denmark Strait also has a cliff or ramp like other terrestrial waterfalls. It is a 3,500 m high ledge on the sea floor near the southern tip of Greenland that was created by glaciers 11,500 - 17,500 years ago, during the last Ice Age. Water from the sea floor flows through the strait, over the edge of the ledge and down its slopes, forming a waterfall beneath the warmer surface waters of the Irminger Sea.

Although the seabed slopes down more than 3,500 m, because it flows into a deep lake containing cold and dense water, the overflow is only about 2,000 m high. The overflow is as wide as the Denmark Strait, spread over 480 km of seabed, so the downward flow speed is only about 0.5 m/s, much slower than the flow speed at Niagara Falls (109 km/h), or 30.5 m/s.

The highest waterfall on land is Angel Falls with a height of 979 m and a width of 150 m at the base, equivalent to 3 Eiffel Towers stacked on top of each other.