For most divers, a pair of fins and a mask are their first purchase after becoming certified divers.
Fins are usually made from rubber, plastic, or some combination of these materials, and are also known as swimming fins or flippers (although your dive instructor probably told you never to call them flippers). Swimming fins are designed to improve the shape of human feet, which are not shaped to be powerful in water; fins provide a means for humans to propel themselves forward with less effort than would otherwise be required.
Swimming fins mimic a fish fin, using the increased surface area to give increased propulsion. There are many different kinds of fins, all of which are suited to different types of swimming; for example, very long swimming fins might be used by free divers and are designed to reduce energy expenditure, which helps to conserve oxygen
Choosing the right fins
Fins are one of the most important tools for a diver, so getting a pair which is right for you is essential. You may find that your needs change as your fitness and experience increases, but always make sure you are diving with equipment which is comfortable.
Fins which are specifically designed for scuba diving are generally long, which offers you good propulsion with minimal effort by combating some of the effects of water pressure and the weight of scuba equipment. Some fins have channels or splits in them to further reduce resistance, so it’s worth looking into the different designs and styles to see what might suit you.
Fins reduce your fatigue and chance of cramp, meaning you can dive for longer, and also enjoy it more. Make sure that they are always fastened securely and not pinching or restricting your feet before going into the water; you depend on them for your speed and movement, so ensuring they are fitted correctly is extremely important.
When choosing the right fin, always remember that with an efficient fin there will be an immediate connection between how much oxygen and energy your body uses and thus how much air you consume. This is especially important for novice scuba divers who will undoubtedly need to save air more than an advanced diver who is more relaxed in the water.
There is a vast array of fins on the market and you will need to consider your level of experience, kicking style and ability, leg power and type of diving you will be doing in order to determine which type of fin will best suit you. Diving fins should neither be too short (like swimming training or boogie boarding fins), or too long (like spearfishing, or freediving fins).
When choosing a fin just remember, the stronger the leg, the longer and stiffer the fin should be. However, fins with rigid sides and a flexible middle made up of different materials will generally provide more thrust power with less effort. Many top end fins will incorporate a number of materials in the blade and foot pocket including carbon fiber, graphite and polymers to maximise the amount of energy transfer from the leg to the fin. Believe it or not, there is a great deal of science that has gone into the manufacture of fins!
Full-Foots vs. Open-Heels
Some scuba fins can also be worn over diving boots, which will help you keep warm if you’re diving in deep or colder waters. These open-heel fins have adjustable straps which will allow for different boot sizes.
Wearing boots offers your feet more protection as well as giving you added warmth. On the other hand, full-foot fins, like the name suggests, cover your entire foot, cannot be worn with diving boots and are generally your best option in warmer waters and short dives or pool training.
Full-foot fins are significantly lighter than open-heel fins and create less drag since they are more ‘aerodynamic’. Full-foot fins also have a tendency to have more flexible and shorter blades, making them easier to kick with underwater. Since full-foot fins are intended to slip over your barefoot, you don’t need to wear a neoprene dive boot either. This helps the rubber foot pocket to grip the foot very firmly, this, in turn, allows for the more-productive exchange of energy from foot to fin.
Getting an ideal fit in a full-foot fin before purchase is critical to efficiency and comfort because the foot pocket can’t be adjusted. Too large, and it will slip off your foot while diving. Too small and the foot pocket will hurt your toes and foot after a while.