Hi Y'all... Capt. Jim checkin' in...

In response to a question and a few answers posted in Aqua Shack Reasoning Room I figured it was time to do a little writing. I hate to admit it, but I gotta agree with Damon to a certain extent on this one (only kidding Damon. I don't really mind agreeing with ya). Marcus & Jason bring up good points too, which may or may not pertain to you.

I've been diving since 1973, let's see that'll be 31 years and well over 5000 dives this May, ... wow, I fee old! In that time, I've tried hundreds of fins as a diver, Divemaster, Instructor, boat Captain and Dive Center owner. I've also bought more than I care to think about in an attempt to find the perfect fin. Unfortunately, there is no ONE PERFECT FIN for ALL divers in all conditions doing all types of diving. So instead I've narrowed it down to a few of MY personal favorites for the types of diving I do. If you want the short answer as to what fin to buy, I'd say BUY 3 or 4 ! One long warm water full foot fin, one open heel long paddle fin for when you want to "crank", one open heel split fin for when you want to move without working too hard, and one open heel short stiff fin if you do wreck/cave diving.

First of all let me say Damon is correct in stating that there are "scientific", hydrodynamic and empirical results of design, thrust & efficiency (thrust to work ratios) tests and then there are "REAL WORLD" results! I tend to trust & believe in my and others real world opinions, keeping in mind a little of the "scientific" results of design & materials testing so I know the "reasons" the fins behave as they do.

Your "real world" results will vary greatly depending on many factors such as; size & stiffness of the blade, design of the blade & fin, your height & weight, your body shape, your leg strength, your kicking style, the other gear you're wearing (wetsuit, drysuit, no suit, amount of weight, etc.), your body position in the water as you swim (attitude: head/shoulders higher than, level with, or lower than your feet), the shape of your foot (effects foot pocket comfort), the type of diving you're doing (wreck/cave vs. open water), currents or how "fast" you want to move, your personal desires as to how hard you want to work that day (some days I want to "crank" others I want to chill out and relax), and probably many more I can't think of right now. Anyway, that ought to give you some idea why there are so many subjective "real world" opinions about what's best! What's my idea of best may suck for you!

With all that said, I've compiled a short list of my favorite fins of all time (some of which are not even sold any more) for various activities and climates.

Wreck/cave diving: Scubapro Jet Fins - Positives - Short & maneuverable, relatively stiff yet quite efficient. It still amazes me that they got it right way back in the 60's before CAD/CAM systems and hi-tec materials. They've changed the materials over the years making it a little more flexible, but the design remains the same. Unlike "copies" that just put a hole in the fin, Scubapro keeps the fin short but actually INCREASES the surface area by having two fin planes, the end of the first overlapping the beginning of the second (the main) by a few inches. If you look at a U.S.Divers, IDI, IST or any of the copy "rocket" fins, you can see right through the hole. True, this makes it easier to kick, but only because all the water spills through it rather than producing thrust. The Jetfin allows the water to pass through, but keeps it going backward before it flows out. This adds a few inches of surface area to the fin without adding length and forces the water out a smaller opening than it entered (hence the "Jet" moniker). This last point is referred to as the "venturi effect" and is a special case of "Bernoulli's Law" to be discussed later.

The venturi effect was used in designing nozzles for steam engines and later for rockets and uses a converging (narrowing) nozzle to speed up the flow of a gas under pressure. The principle also holds true for fluids as well as gasses. The venturi effect is seen when water is pushed at high speed through a nozzle. It all has to do with the "conservation of energy" principle. As a volume of water (or any fluid) is pushed through a narrowing nozzle, the speed of it MUST increase to allow the same volume of fluid to pass out through the other end. The venturi effect is also the effect we see when a current of water enters a narrow passageway; like the incoming tide under the "Blyman Canal" in Gloucester. The venturi effect is a very "efficient" principle to apply to fin design since it allows extra down-force to be created with little or no increase in drag. Enough of the science lesson for now.

The only negative I have with the Jetfins is the foot pocket design. if you look at it from the end, its almost a rectangle. The top is very flat. If you have high arches or use big thick drysuit boots this puts extra pressure on the top of your foot and can hurt after a while. For me this wasn't much of a problem until I did start using them with a drysuit. They really began to hurt and actually cut off feeling to my feet after a while. To fix it I heated the footpocket with a heat gun, stuck a beer can inside and let them cool to the new "rounded shape". It worked awesome! I told Scubapro about the problem and my fix, but they still haven't done anything about making a slight change to the mold. Whatever! I got mine...

As a second place finisher I go quite often with the Scubapro Splitfin (the Black one... it's a little stiffer than the other colors). I don't see what some people say about not getting enough maneuverability out of them. I think they work fantastic with a frog or modified frog kick. Another plus is that they disturb very little water (and therefore silt) on the up and down strokes when inside a wreck. The water is all sent rearward because of the split. Also, even though I've heard some people say they don't have the power/thrust of a paddle fin, I have three observations 1) you're not usually flying around inside wrecks anyway... you're going slow and purposeful, and 2) I think they give you the same speed (if you need it on the outside of the wreck) as a Scubapro Jetfin, it's just that you don't feel like it because your kick is so much easier. It's like a mental thing... "I COULDN'T be going as fast... it's too easy". Lastly, 3) as Damon mentioned the kick cycle is definitely different. To get more speed out of them, rather than kick harder and wider (as with a paddle type fin), you do MORE and faster kicks, but still no wider than the width of your body and gear.

Think of the difference between an old paddle wheel steamer and a modern propeller. With the old paddle wheel, you notice it moves very slow. There is a huge paddle moving large volumes of water so it's very difficult to make it move faster. To increase speed it takes lots of energy (more steam power) to get the paddle to turn faster. This is like your leg... you "feel" the stress on your thigh muscles of "harder" kicking with a paddle fin. With a modern propeller to increase speed you increase the throttle and the prop spins faster thus increasing the velocity of the water exiting behind the boat. A similar principle applies to the Split fins. Another way of thinking about it is, it's like riding your bicycle in 1st gear rather than 10th gear and trying to cover the same distance. In 10th you're peddling much slower but feeling the resistance much greater than in 1st, where you peddle many more revolutions but feel much less resistance.

The only negative to them is, again, the shape of the foot pocket is rectangular and suffers the same problems as the Jetfins... it hurts the top of my foot. Fortunately I applied the same fix and now they fit like a glove... er... I mean boot! Scubapro never has gotten a foot pocket right... I think everyone over there on their design team must have square feet!

"Warm" Open Water Diving: Mares Avanti Quattro HP Full Foot Pocket - Positives - Hands down the best warm water fin for open water diving is the Mares Avanti Quattro full foot pocket fin. It is relatively long with fairly stiff side rails tapering to a more flexible side rail toward the end of the blade. The Quattro Avanti has 4 very flexible "membranes" that when kicked produces a cupping action to prevent water from "spilling" over the side rails so more water is directed rearward producing great thrust (for every action there is an opposite and equal reaction). It mimics a seals fin quite nicely; and we all know how agile a seal is in the water. It has, I think, the most comfortable full foot pocket on the market which is most important, especially on a full foot fin where you're not wearing boots, but rather are bare foot.

The only negative might be... hell, I can't think of any... I love this fin! I was going to say it can be a little "too much" fin for some people as it moves a lot of water, but this is easily overcome by most any diver with any kind of leg muscles just using a more relaxed, slower, longer kick. In other words, if it feels like your working too hard and your legs are getting tired, slow down and take it easy! You can do that with this fin and still get very decent thrust. Some fins like the old Mares Avanti are just stiff, stiff, stiff and they're always hard to kick whether your kicking hard or trying to relax a little and kick them easy (and in that case you won't go anywhere). If you want a really easy kicking fin get a splitfin!

Cold Open Water Diving: I choose 3... In MY order of preferance 1) Atomic Aquatics Splitfin, 2) Scubapro Splitfin and 3) Mares Quattro Avanti. For me it all depends on what I'm doing (photography vs. scallop diving for example) and how hard I want to work that day. I usually bring them all and decide at the last minute based on conditions and how I feel at the moment, and to be honest I usually end up going MOST OFTEN with the Atomic Aquatics Splitfin... it's a awesome compromise between the Mares Quattro Avanti and the Scubapro Splitfin. Let me say this first; I know not everyone is an owner (or former owner) of a diveshop and can buy all these fins, so if you can buy only one fin for all your Cold Open Water diving, go with the Atomic Aquatics Splitfin, you WON'T be disappointed.

I already described the Scubapro Splitfin in plenty detail above under the wreck diver fins. Well, it also makes a great Open water fin as well, especially if you're doing photography or want a nice relaxing, easy kicking dive, but still want to "move" every now and then. I also described the Mares Avanti Quattro in full foot pocket version for warm water diving. Well the same principles hold for this fin in it's cold water open heel version. Rather than getting a nice easy kick, you definitely "feel" this fin. If you got the leg for it, it cranks... moves lots of water and will get you there in a hurry with a good hard kick!

It is my opinion though that the Atomic Aquatics Splitfin is the best of both worlds. Longer and stiffer than the Scubapro Splitfin, it gives those of us that feel the Scubapro Splitfin is too "floppy" more resistance. This way you "feel" your kicks a little more, which many people like, especially us old timers that are used to stiff fins. You don't feel like you're kicking your brains out and not getting anywhere. On the other hand though, they are MUCH easier kicking than the Mares Quattro Avanti, a nice bonus when you just want to take it a little easier.

I've noticed as I got older I began to use my Quattros less and less, I just wasn't in that much of a rush anymore and quite frankly didn't want to work that hard! At first I went to the Scubapro Splitfin, and loved them... they were great. But as I said I was used to a fin with a little more "feel" to them, and actually, I prefer it that way. Then the Atomic Splitfin came out and I was sold! As I said... an awesome compromise. It gave me an easier kicking motion, relative to the Quattro, the stiffness I was looking for, could be kicked light and easy for a relaxed dive or "pumped up" when I wanted to crank or had to fight currents, AND has an EXTREMELY comfortable (rounded shape like a foot, not rectangular) foot pocket which comes in a TRUE XL for drysuit boots!

The ONLY negative is the ski boot style buckle which is a weak point waiting to break. I've broke a two (now I carry extras). I broke one when I threw my fins up onto the rocks once (I don't do that anymore), and one when my foot got bashed into a rock making an exit at Catherdal in rough seas. I do believe Atomic is coming out with another buckle, and there are other manufacturers buckles that are simpler in design and less likely to break that fit also. I still feel that this slight drawback is minor in comparison to all the benefits the fin offers, and is my choice for an all around Cold Open Water diving fin!

In closing I can't write an article on fins without mentioning MY FAVORITE FIN OF ALL TIME!!! Again from Scubapro, and again they had the same poor foot pocket design (rectangular with a flat top), but if they were still sold today I'd buy a pair in a second and try my "heat them up and remold them fix" I used on the other Scubapro fins. I wish I thought of that fix years ago. The fin is no longer made and most of you new diver probably never heard of them, but some of you older divers may remember the Scubapro SEA WING.

These fins were way ahead of their time. They had no leading edge to disturb water flow over the fin, a design now used on Scubapro's new Razor Fin. They also "hinged" to keep the angle of attack of the blade in the best position, a design feature now used on the Mares Volo fin, but without their hinge/joint arrangement which breaks. The were fairly short and slightly wide and, like the Jetfin, had the two overlapping blades that allowed water to pass through making the kick a little easier while INCREASING blade surface at the same time!

These fins truly worked on Bernoulli's Law. That is ... For horizontal fluid flow, an increase in the velocity of flow will result in a decrease in the static pressure. The equation describing this effect is known as Bernoulli's law. For a complete explanation see http://scienceworld.wolfram.com/physics/BernoulliEffect.html and http://scienceworld.wolfram.com/physics/BernoullisLaw.html . The most practical example of this is in the action of an airfoil. The shape of an airplane wing is such that air flowing over the top of the wing must travel faster than the air flowing under the wing (to cover the same distance and exit at the foil end), and so there is less pressure on the top than on the bottom, resulting in lift. When swimming horizontally in water this lift is manifested as forward motion.

When they first came out many people thought they were ugly ass fins because the blade was rectangular which was a huge departure from the norm, and people just couldn't get over that. But now-a-days there are find of all shapes and man... just thinking about them makes me wish they'd come out with them again... but with a better foot pocket of course. You can still find a pair or two on Ebay every now and then, but that's about it. As a matter of fact I just bid on the only two XL's I found listed on Ebay, and if I get them, I'm gonna try to remold the footpocket. I can't wait to try them out ... again!

Well that's it! I had fun reminiscing about my favorite fins and hope I was of some help to those of you looking to purchase a new pair. Peace Out & See you underwater!

Capt. Jim

"One Love, One Destiny. One Earth, One Chance! Symbiosis"