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The importance of fins in scuba diving cannot be stressed enough. A diver wearing full gear, including a wet suit, is unsafe in the water without fins. Trying to swim with just your arms is very strenuous and, as swimmers experience in a pool when they try to swim a length using the legs only, propulsion without moving the arms is very, very difficult. The author once saved a diver that entered the surf with his fins under his arms. A wave knocked the diver over, the fins were lost, and he floundered in the sea and almost drown before being pulled to shore. The ability to comfortably move about while diving is made possible by the use of fins!
The proper name is, "fins." Flippers are found on pinball machines and in the list of names for dolphins.
Basically there are two types of fins: Full-foot and adjustable. Full-foot fins are worn on bare feet and they cover the entire bottom of the foot. Adjustable fins have a strap in the back that can used to tighten the fin on the foot. Adjustable fins are usually worn over wet suit boots. Most divers wear the adjustable fin with the wet suit boot even in warm water. The fin and pocket is usually larger, and because of the boots are more comfortable on the foot. Full-foot fins must be fitted properly and are not as forgiving to the foot if they are not. A full-foot fin that is too loose can result in painful blisters. Also, since there is no protective boot, any rubbing points on the fin can be annoying. However, full-foot fins cost about 1/5 of what it would cost to buy the adjustable ones with boots. However, if you do have a pair of full-foot fins that are too large, wearing cut-off socks might prevent problems.
There is always the question of how and when to put the fins on for diving. The answers really depend on the diving situation. In all cases, be sure there is some air in the BC prior to entering the water! The following may help to clarify the issue:
When the fin is on the foot and it is necessary to move from one place to another walking backward is the easiest. Trying to walk forward is difficult because of the length of the blade. If the diver is going a long distance, or is in crowded quarters, it would be better to move without the fins on the feet.
Kicking underwater with fins on requires proper technique. The power of the fin comes from the downstroke almost completely. High pressure is created on the down side of the fin because of the increased number of water molecules that are ecountered and have to be moved aside. The up side of the fin would have a lower pressure. The high pressure pushes the diver forward. Incidentally, the molecules that are pushed away from the downside of the fin is called drag. The recovery of the leg to the up position provides little thrust. To get the most power out of the kick, the knees should be bent very slightly so that most of the power comes from the muscles in the rear end. When one kicks from the knees it is called a "bicycle kick." It produces very little forward motion, exhausts the diver, and looks stupid. The kick should be from the hip and the legs should move a great distance up and down. It should be relaxing and leisurely, unless you are being chased by a shark.
When you buy fins be sure to try them on prior to the purchase. If you are going to by fins through the mail, over the Internet, etc. make sure you know the exact size and brand prior to doing so. Fins are like shoes. If they don't fit properly they can damage the foot. And, to get the size and the brand you have to try a pair on.
When not being used fins should be stored properly after rinsing with fresh water. Do not store them in a hot place, resting on the blade, or with objects on them. Thermoplastic fins may permanently change their shape.
Check the straps and buckles prior to each dive. Remember, a diver scuba diving without one or both fins is in a dangerous situation!
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