Monofin

A monofin is a type of swimfin typically used in underwater sports such as finswimming, free-diving and underwater orienteering. It consists of a single or linked surfaces attached to both of the diver's feet, emulating the fluke of Cetaceans like whales or porpoises. Even though the diver's appearance might be reminiscent of a mermaid or merman, monofin swimming is not the same as mermaiding.

The arrival of the monofin in the early 1970s led to the breaking of all finswimming world records by the end of the decade due to the improved performance possible when used instead of two ordinary swimfins.

To differentiate between the use of monofins and conventional fins, the latter are sometimes referred to as stereo fins or bi-fins.

The monofin swimmer extends arms forward, locking hands together, locking the head between the biceps, in a position known as streamline position. The undulating movement starts in the shoulders, with maximum amplitude towards the hips; the legs almost don't bend to transfer the movement to the monofin. This technique is called the dolphin kick.

By slowly oscillating the surface of the monofin when submerged, divers can generate large amounts of thrust even with small or slow movements. This preserves energy which helps when breathholding (apnea).

Monofin kick tempo doesn't have to be slow. In 100 m surface swimming, tempo is around 2 kicks per second.

Separate from its functional use in swimming or diving, monofins may be used ornamentally, as part of a mermaid costume.

1949: Kurt Schaefer, who invented an underwater film camera during wartime military service in Italy, designs a pair of homemade swimming fins, which he proceeds to fasten together with straps and cords to create what is probably the world's first monofin. The artefact is on display in the Aquazoo-Löbbecke Museum in the German city of Düsseldorf.