Back in the sixties, there used to be a tv cartoon show called "Marine Boy". Marine Boy didn't have an aqualung or a rebreather, he had oxygum. Oxygum probably wasn't made by Wrigleys, but it should've been. Unless the US Navy has been feeding this stuff secretly to SEALs, it is still a hand drawn frame in someone's imagination.

Marine Boy also didn't need to swim. The same animator had thoughtfully put a couple of propellers into his wetsuit boots. With these Marine Boy whisked around the underwater world seemingly untroubled by either dud batteries or stop signs.

The egg whisks have, in fact, made the leap to reality. Divers really can buy strap on leg propellers. But for most of us, simple kicking will have to do. Motordrive simply isn't realistic and we have to resort to what a friend of mine calls "Rubber Engines" - or fins.

Fins were first described hundreds of years ago. But from the sport divers point of view, the real thing didn't appear until the early 20th century. They originated from the South of France where the sport of "Goggling" had begun to catch the imagination. Their inventor was a Commander De Corlieu.

Nearly a century on and the power source has not changed, but fins themselves have altered and evolved greatly. In this article we'll look at the different requirements of undersea explorers from holiday snorkellers to freedivers to underwater hockey players and recreational scuba divers.

Many of us become addicted to diving through snorkelling on holiday. For snorkelling in good conditions with little wave action or current, the best fins tend to have fairly flexible blades. These are easy to get used to and don't require you to be a conditioned swimmer. As a snorkeller you'll spend most of your time on the surface. The flutter kick works best here. Any part of the fin that breaks surface isn't contributing to thrust - the force that powers you through the water. So the kick, which comes mostly from your hips with little knee action, is quite shallow. It's similar to the flutter kick used in the crawl.

Snorkelling fins usually have foot pockets that cover your foot and slide on like slippers. They are sized like shoes. The toes are left open for comfort and to allow any sand that enters the fin from the beach to exit easily before it causes discomfort. Soft rubber is the usual choice for the foot pocket. The blades may be rubber or plastic. It tends to take a lot of kicks to get anywhere with these kinds of fins. But the flexible blade makes the fins easy to get used to quickly, so you are unlikely to get cramps and , frankly speaking, you don't need to be especially fit to use them. For young children whose leg muscles are much less powerful than an older teenager or adult, this can be an important benefit.

Freediving is a newish term used to describe serious snorkellers. Freedivers tend to engage in deep snorkelling and competitive breathold events involving deep diving or underwater distance swims as well as spearfishing. These divers routinley snorkel in the 25 to 35 metre ranges. To make such demanding dives that may see participants holding their breath for two to three minutes at a time, freedivers do everything possible to minimise effort. A lot of oxygen is burned by finning, so reducing the need to fin prolongs the dive time.

Freedivers normally use long fins designed to propel them long distances with each kick. This economy of movement reduces the powerful draw on oxygen reserves that finning creates.

Freediving fins usually use either plastic to form the blades or graphite. Different levels of stiffness are offered to suit individual divers preferences. Because the combined length of the blade and foot pocket can make packing the fins difficult, they can usually be seperated for travelling.

Freedivers talk about stereo and mono fins. Stereo are conventional paired fins. Monos are single fins with large wide blades designed to be kicked using an undulating motion, much like that of a dolphin.

Underwater hockey players are another distinctive group with a requirement for a specialist fin. The fast moving game, played with a bat called a pusher and a lead puck called a squid sees two teams fighting along the pool botton for posession of the puck. It's violent. Underwater hockey players need fins that let them turn and twist virtually instantly in the midst of a scrum.

Scuba divers have less requirement for speed than freedivers and underwater hockey players. But they need efficiency to drive them through the water against the drag of their cylinder set or rebreather. Because they are normally fully submerged, they can use a much wider scissor kick and modern fins take advantage of this.

The widest range of fin styles is sold for scuba divers. Vented fins were one of the first innovations in scuba. Developed by Beauchat of France and franchised out, vented fins go back to the 60's. One problem faced by divers was that if you made a fin blade simply larger, the sheer stiffness of the rubber made it very hard on your legs. This was not so bad on the downstroke, but much tougher on the recovery kick. With vents the fin blade carves through the water on the downwards power stroke and the slots have little effect. Most of the blade appears "solid" to the water and creates thrust. On the weaker up stroke water flows through the slots reducing fatigue. Traditional vented fins are still sold, although they are probably best suited to conditioned swimmers.

During the late 70s new polymers were applied to the design of fin blades. This meant blades could be manufactured in a much lighter material than traditional neoprene rubber fins. They could also be given better "flex" properties.

Split blades have been around for about a decade.

Some blade designs work well for speed, but may not be so efficient for sculling backwards or precision manouvering.

Like most things in life, the fin you eventually choose is likely to be a compromise. Some divers find that they need different types of fin to cover the range of activities that they enjoy. For example they may own both scuba and freediving models.

Fin blades come in a range of colours. And, actually, there's more to choosing the hue than simply fashion. Photographers sometimes use white fins as a target for setting the white balance on their cameras. Spearfishermen may select low visibility greens to better merge with natural cover like weed. A diveleader might choose a colour that's distinctive, or even use different blade colours, to help his group identify him easily.

A bright coloured fin can also be used on the surface to attract the attention of the boat by waving it overhead.

A combination of using the right fins for you, proper streamlining and good buoyancy skills will help make you an efficient diver. You'll tire less, use less air and enjoy longer, more comfortable dives.

Open back fins are designed to let a diver wear boots to protect their feet from rocks and other hazards found around dive sites, and to allow for insulation to keep your feet warm in cold water. The foot pockets need to be large enough to accommodate your boots. If you use fins designed for boots without them, you'll likely cut your feet. As I have done.

Some fin pockets feature a moulded plug in the sole. By punching this out you leave a hole. This can help prevent vacuems that will make it hard to take off your fins at the end of the dive. The hole also lets air run out as you duck dive. This stops large bubbles of air leaving the fin pocket in one noisy go and frightening marine life. So spearos often take advantage of this feature.

It is important that you can remove your fins yourself. Many divers find this difficult. This is potentially quite dangerous. Hanging on to a pitching boat ladder and holding up other divers in a short chop can easily lead to injury.

Fin designers have tried a number of ways to make fin straps both secure in use and then easy to release. Some use quick release buckles, similar to those found on many BCD harnesses. Others used hinged designs that open up to slacken off the strap. Stainless steel springs are also used. These are effectively unbreakable and easy to put on and take off. A home made alternative is to use bungy card.

Fin straps are consumables. Eventually they perish and snap. They usually do this as you put them on. As fins are usually the last piece of kit you put on, it will inconvenience both you and your buddy. It will cost you time to unthread the broken strap and rethread a spare one. If you are trying to dive to a specific point in the tide, either to hit slackwater or catch a current for a drift, this might mean you miss your dive.

It's a good idea to keep a spares kit in your BCD pocket for these emergencies. With many fin strap designs if you have a strap and male buckle ends already fitted, you can replace the broken fin strap in seconds and you and your buddy can get on with your dive.

Amos Nachoum, the celebrated and audacious big animals photographer, sometimes leaves his fin straps off. His reason - in Antartica he has been under the ice cap photographing Leopard Seals. The seals predate on Penguins and have long sharp teeth. Like many seals species they are playful around divers and often bite at their fins. His concern is that if a seal, much larger and stronger than any man, get its teeth caught in the fin it will panic and bolt. Better to lose the fin than be towed off into the deep and away from your exit hole.

Can you really learn to use fins? Actually efficient fin use is very much linked to good buoyancy control, trim and streamlining. Special finning techniques are useful for penertation diving through overheads to minimise silting and entanglements in guide lines or stray cables often found inside wreckage. Learning how to scull backwards can be an essential skill if your hands are full of cameras.

Fin tips have no nervous system. So it's very easy to damage delicate corals either through direct impact or churning up the sand and smothering the polyps. Precision buoyancy courses teach spatial awareness and special finning techniques that will help youavoid this. These skills will also help you to avoid destroying the visibility in confined areas like wrecks and caves where being able to see is helpful. You'll also learn to avoid entangling your fins in safety lines.

Fins deserve much more attention in their selection that they usually receive. And don't be shy about paying premium prices for a good pair. Even the most expensive fins cost far less than a pair of chic italian loafers and many compare favourably with decent running shoes.