Fins increase the size of your foot, allowing you to move more water and therefore to move more effectively underwater. Fins are attached to your feet because your leg muscles are stronger than your arm muscles and therefore tire less when you use them to propel yourself forward. Fins also free your hands on a dive and provide a surface of resistance which stabilizes you underwater.
Fins are available just about everywhere – including children’s toy stores and general sports stores. However, fins vary very widely in quality and style, so it pays to buy your fins from a quality source. Fins help you move about the in water and can affect the overall quality of your dive, so it is vital to get the right pair of fins for your needs. In order to do this, you need to consider:
1) The type of dive you will be taking part in. If you are snorkeling or swimming, you may need a shorter fin and a pretty simply design. If you find that your fins are getting in the way on a swim, that is a sure sign you need a smaller, simpler pair. Scuba fins tend to be slightly longer than snorkeling fins and tend to offer more propulsion power. Free diving requires longer fins, since free divers are heading to significant depths without air supply. The fins need to allow the diver to get the most power from each kick so that the diver can move further while using less air.
2) The type of water temperature you will encounter. If you dive in cold water, you will want boots and other cold-water diving gear, which means that you will need open-foot fins with a heel strap around the back. This style of fins is a must when you wear dive boots and allows you to adjust your boot and fin together for a comfortable fit. If you have thick-soled dive boots, especially, an open-foot pocket will easily allow your boot and fin to fit and work together without slipping. If you dive in warm water, a closed-foot fin design may be ideal. It will offer your foot some protection without you having to wear boots, since the closed-foot fins fit like a slipper over your whole foot.
3) Fit. Your fins need to fit correctly with your foot and with any foot gear you may be wearing on your dive. If your fins scrape or rub against your ankles, they are too big or generally a poor fit. If your feet feel pinched or start to tingle when you wear your fins, your fins are likely too small.
4) Channels. Channels are a nice feature available on many modern fins. Channels help divers move more quickly by offering less surface area resistance. Some channels are placed to create more flexibility on the fin surface. This also enhances speed by allowing the fin to bend more and therefore move more water with every movement.
5) Split fins. Some fins feature a split, which is designed to help improve the effectiveness and power of each kick. The idea is that water channels through the split with each downward move of the fin, and this creates a spring-like action which makes movement more powerful and reduces diver fatigue. Some divers claim that split fins reduce resistance on the joints, which is why these fins are every popular with divers who have knee problems.
6) The blade. The stiffer and larger the blade of your fins, the more work you will need to do to move through the water. For many recreational divers, a medium size and a medium stiffness offer the best propulsion power with the lowest level of fatigue.