Deep-Six Underwater Systems, Inc.
"Add Depth to Your Life"

Table of Contents

1 Pressure and Gases
2 The Face Mask
3 The Snorkel
4 The Fins
5 Weight Systems
6 The Knife
7 The Wetsuit
8 Pressure and Water
9 The Ear and Pressure
10 The Sinus and Pressure
11 The Stomach/Intestine and Pressure
12 The Lung and Pressure
13 Barotrauma caused by External Air Spaces
14 The Buoyancy Compesation Device (BCD)
15 The Scuba Cylinder
16 The Scuba Cylinder Valve
17 The Regulator
18 Density and the Diver
19 The 4 Gas Laws
20 Hand Signals
21 Carbon Monoxide Poisoning
22 Hyperventilation
23 Nitrogen Narcosis
24 Diver's Flags
25 Sound Underwater
26 Color Underwater
27 Decompression Sickness
28 Breathing Oxygen
29 Deep Diving
30 Thermoclines
31 Thunderstorms
32 Underwater Life
33 Open Water Dives
34 The Final Examination
35 The Environment
36 Advanced Course

4 - The Fins

     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:

  • Boat Diving: If you are going to enter the water from the stern of the vessel, keep the fins in your hands until you have gotten to the stern, sit down, and put them on. A diver should not be walking on a boat with fins on their feet unless there is plenty of room to avoid other divers. If you are going to enter the water from the gunnel (side) of the vessel, donn everything, get up on the gunnel,  put your gauges between your legs so there is no issue with the cleat, and then do backward roll.
  • Beach Diving with Surf: Carry the fins to the edge of the water with all the gear on except for the gloves and the fins. Using your buddy for support, donn the fins. Donn the gloves and walk into the water backwards. Try to time the entry to go between the breaking waves.
  • Beach Diving with Calm Water and No Underwater Drop-offs: Carry the fins and gloves into the water to water that is waist deep. If the water is cold put on the gloves before the fins, otherwise do it in reverse. Get your leg into the "figure 4" position and the fin strap below the fin. Put the fin on the foot and pull the strap up around the heel and into position. Do the same for the other foot.
  • Beach Diving with Calm Water and an Unknown Bottom: DO NOT GO IN THE WATER WITHOUT THE FINS ON! Follow the directions (above) for Surf Beach Diving.

     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!

Copyright Information about this text, DIVING WITH DEEP-SIX is as follows: Copyright 1996 - 2007 by George D. Campbell, III; President. All Rights Reserved. This file may be posted on Electronic Bulletin Boards for download, but may not be modified, printed for distribution, or used for any commercial purpose without the author's written permission. is using this material with the permission of Deep Six. The full version is available at:
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