They may look funny and make you walk like a penguin, but scuba fins are highly engineered pieces of precision gear. Different fins are designed for different types of diving, so a scuba fin that is appropriate for gentle drift diving around the Gili Islands may not work well for cave diving. There is a nice article about it: http://divebuzz.com/how-to-choose-dive-fins/.
Years of research have been devoted to developing different fin materials and designs to maximize fin propulsion while minimizing kicking effort. Learn about the different styles and features of scuba diving fins before deciding on a scuba fin purchase.
When choosing fins, always remember that with an efficient fin, there will be a direct correlation between how much oxygen and energy you use and how much air you use. This is particularly important for novice divers who will no doubt need to conserve air more than an experienced diver who is relaxed in the water and already has sound air consumption. As with masks, your primary concern when purchasing fins should be fit and comfort.
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 spear fishing fins). As a general rule, 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 maximize 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!
As a general test for blade stiffness, if you turn a fin upside down with the foot pocket at your shoulder and fin tip held by your fingers and bend the fin 90 degrees, it should be reasonably difficult to maintain in that position. If the blade flexes too easily it will not offer enough power for you, whilst, if it is too stiff and difficult to maintain in a 90 degree position, the blade is likely to be too powerful and difficult to use. Note this test is not possible on a split fin blade, where split fin selection criteria should be based on rigid sides, a blade with at least 2 materials for flexibility and grooving in the blade to enhance water channeling.
Full foot versus open heel?
Despite the vast array of choice on the market, there are just two main styles of foot pocket – open heel and full foot. Both types of foot pocket will come with an array of options for blade.
Full foot fins are usually cheaper than open heal fins, easy to don and less bulky, however, if they are not a perfect fit for you will cause lots of friction issues and blisters. Never compromise, always go for fit when selecting full foot fins. Do not be talked into buying wet suit socks to ensure a proper fit for full fit fins or be tempted to purchase full foot fins where your toes feel cramped because they are on sale! Ideally, you do not want the top of the foot pocket to come too high on your instep as this may result in friction and chaffing. If the fins feel comfortable and a good fit, try standing up on your tiptoes whilst wearing them, if your fins stay on at your heel, they will not fall off in the water. Quite simply put, if full foot fins do not fit perfectly do not purchase, you are wasting your money and will live to regret your decision.
The downside of a full foot fin is that is the water is cold, they do not offer any thermal protection for your feet. Another negative is, if you are shore diving, you will need to consider where you will be walking as, without boots, your feet will be vulnerable over rock pools and similarly on hot dive decks.
As a result of the restrictions on full foot fins, most divers tend to go for an open heel fin type where a neoprene dive boot or dry suit boot is required to be worn underneath. Open heel fins are more adjustable, comfortable and versatile than full foot fins and provide cushioning and chafing protection, but tend to be bulkier, more expensive and can have complex strap adjustment mechanisms. An open heel fin worn with a dive boot will offer thermal protection in colder water and given that water is a much better conductor of heat than air is, I have never complained about my feet being too warm in tropical waters! Versatility is key with an open heel fin, the same fin being able to be worn with a pre-fitted dry suit boot or even a pair of trainers (yes, I have seen this!), eliminating the need for multiple fins being required in different conditions. Open heel fins also have the added advantage of providing additional stability and maximum propulsion.
In terms of fit, open heel fins need to feel as though they are holding the boot and the foot in the foot pocket. The foot should not feel as though you can wiggle it easily from side to side and similarly not too much of your boot should stick out of the bottom of the foot pocket. Whilst fit will vary between style and manufacturer, most manufacturers will provide a shoe size range as a guide for each fin size to make fitting a little easier.
Blade type – split fin versus paddle blade?
Ask any experienced diver or dive professional this question and it will undoubtedly provoke a lively discussion! Whilst paddle blade fins have been around for many years, split fin technology is a relatively recent addition to diving.
The whole idea of a split fin is that the blade causes a vortex in the water as you swim along. Also, on the divers upward fin stroke, where minimal propulsion is achieved in any fin, the split blade opens up and allows water to easily pass through. These features essentially provide excellent propulsion for less effort and ensure that a split fin is more efficient than a paddle fin. In essence, split fins are easy to use and as a result, many divers find that they can conserve up to 40% more air with a split fin over a more traditional paddle blade. People who suffer from cramping, are injured or have weak knees, ankles or back problems will benefit from using split fins because they are so easy to use. Splits also make an excellent snorkeling fin, allowing you to conserve energy and ultimately stay out longer and see more!
Many new or inexperienced divers have ineffective fin techniques (“the bicycle kick”) or are simply not good swimmers. Regardless of your fin technique, with a split fin, you will get somewhere efficiently and this makes the split fin an excellent option for novice divers.
With all these positives for split fins what is the catch I hear you say? Well, whilst split fins may be more efficient than paddle blades, they are not as powerful. What this means is that whilst split fins may be easy to use when the conditions are good, when the conditions turn, you simply will not have the power that a paddle blade fin can offer. In any sort of current, give me my paddle blade fins any day over splits! Because of the extra grunt that a paddle blade will offer, they tend to be the preferred option for most dive professionals when power is key for chasing students, conducting rescues and so on.