The use of plastics in fin manufacture has fostered the development of fins which some divers consider to have improved characteristics. Plastic can be lighter in weight than the more traditional rubber, with controlled and predictable flexibility. It is durable and economic to produce and has proved to be a popular component of current fin design.
Fins are produced in a variety of shapes and sizes designed to perform different functions and from a variety of rubbers and polymers. Three examples are shown here. The monofin (1) is a type of swimfin typically used in finswimming and freediving. It comprises a single 'blade' attached to foot pockets for both feet. By oscillating the surface of the submerged monofin divers can generate large amounts of thrust whilst expending comparatively little energy which helps freedivers with breath holding. In finswimming competitions, divers can achieve speeds of up to 12km/h. In training the monofin strengthens abdominal, dorsal and trapezoid muscles and improves lung function. This example is manufactured by Sweammer of France. It comprises a flexible polypropylene blade, polypropylene stiffeners and a soft elastomer open heel.
The split blade is designed to slice through the water with reduced drag thus creating lift and improving forward propulsion. The Splitfin® (2) enables the user to swim with less effort whilst reducing stress, strain and muscle fatigue in comparison with use of the conventional fin. Tests have shown that using the Splitfin® design can significantly reduce air consumption. This example is fitted with a quick release Spring Strap made with rust resistant stainless steel. It is manufactured by Atomic Aquatics Inc. from a high energy polypropylene fin incorporating a rubber foot pad.
These familiar shaped fins (3), designed to be used for snorkelling, have blades made from flexible polypropylene which is moulded onto thermo rubber foot pockets and side rails. Water is channelled over the fin and the blade is positioned at the top of the foot pocket which minimises water resistance in use. They are manufactured in Italy by Cressi.