Imagine an aluminum tube, a sort of “broom handle” with a belt to tie around your waist at one end. At the other end, however, there are two pedals and a bicycle chainring whose chain is connected not to the rear wheel but to a light but very efficient propeller. In practice, those who swim on the surface freestyle while snorkeling do not slam their feet but hold this support between their legs, pedal and travel at an unthinkable speed. It is even possible to attach this structure to a special SUP board for floating and pedaling while seated. It's called SeaBike and is sold all over the world (www.seabike.com)