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DOL-Fin is designed to let you swim like a dolphin


July 11, 2014

The DOL-Fin is a hydrofoil for your feet

The DOL-Fin is a hydrofoil for your feet

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Besides being able to fly like a bird, many people fantasize about having the ability to swim like a dolphin. Divers already have the option of replacing their two regular swim fins with one fluke-like flexible rubber monofin, although aerospace engineer Ron Smith claims that his invention is much more effective. Known as the DOL-Fin, it incorporates a wide rigid hydrofoil-type fin.

There are actually several models of "Dynamic Oscillating Lateral"-Fin, designed for different applications (such as freediving or recreational scuba diving) and levels of performance. In all cases, however, the feet are held firmly in place using either straps built into a foot platform, or attached Shimano cycling shoes.

An elastomer/nylon composite suspension frame connects the fin to the feet, allowing the fin to pitch up and down in the same way that a dolphin's flukes change pitch as it swims. The fin itself is made from rigid aluminum, although most models also have swept-back flexible rubber tips.

The exact physics by which the DOL-Fin is claimed to work are pretty complex, but the basic idea is that the rigidity of the fin and the foot attachment setup minimize wasted energy, while the fin's ability to pitch keeps it from "stalling out" as it arcs through the water. Additionally, the fin's wide design gives it a larger effective surface area than old-school monofins, plus its hydrofoil design is simply more hydrodynamic.

Although some versions of the DOL-Fin have been around for a few years now, Smith is currently putting the finishing touches on his Orca Mk2 model. It sports a streamlined design, along with some other features aimed at competitive freediving.

"The DOL-Fin Orca Mk-2 offers competition level monofin performance, with recreational levels of comfort," Ron told us. "It is made from incompressible materials (no foam), so the fin's buoyancy and swimming characteristics do not change with depth. It has adjustable foot straps that easily allow it to adapt between warm and cold water diving, eliminating the need for multiple monofins for different conditions. It has a modular design that is lightweight and easily packed into standard luggage for traveling."

He hopes to begin selling it within about six weeks, at a price of US$1,200. If you're on more of a budget, or simply aren't a competitive freediver, prices for some of his older, simpler models start at $680.

The Ciamillo Lunocet

Perhaps not surprisingly, Smith isn't the only person making and selling this type of product. Designer Ted Ciamillo also hand-builds a monofin known as the Lunocet (pictured above), which works on much the same principle as the DOL-Fin. The fin itself looks more like a dolphin's flukes, though, as opposed to a hydrofoil. Pricing for it starts at US$299, which doesn't include the required cycling shoes.

You can see the X-15 model of the DOL-Fin in use off the shores of Kauai, in the video below.

DOL-Fin product page: Smith Aerospace

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

This item can only be truly considered a success when it enables divers to leap out of the water, do a somersault and catch a fish in their mouth at the same time.

Mel Tisdale

Nothing like making yourself look even more like a slow and somewhat ungainly lunch for a hungry aquatic predator... The concept is solid but I wonder whether attaching to the lower leg would eliminate ankle flex and calf muscle fatigue, resulting in a more efficient mechanical transfer of energy? Additionally, this has got to be a superior core body workout, so expect a six-pack to one of the benefits.


What a disappointing video. I can't imagine anyone wanting to buy the product after seeing this. I was expecting to see a diver zipping through the water at high speed. This bloke seemed barely able to move his legs.


It is a poor video, very little time devoted to the product and information of. But, I am still interested in the hydrofoil.

Art Toegemann

windykites1 and Art have the right of it. The only way that the X-15 video could have gone from 97% to 100% pathetically useless (a daunting but not impossible task) is if it had been shot entirely from the diver's perspective, thus not showing the DOL-fin device at all. BTW, for those who remember the storied history of the X-15 rocket plane, having this product be something of a namesake is both an insult to the experimental aircraft and an embarrassment to the product, at least as shown in this video.


In the 1960's Cal Gongwer invented a fin mounted on a framework with a front wing and a rear wing on a frame work which used the lower leg pivot . It allowed him to pull 2 frogmen on a surfboard from Catalina island to the mainland when he was more than 40 years old. In films the user could actually porpoise though not catch a fish in her mouth.


The article does not make it clear as to which product cost $299.oo and which are at $1200.oo and $680.oo. Gizmag is always showing products which are completely overly priced. Any or all of the products combined are not worth the lowest price of $299.oo except for those that money is not an object. A person could take the planning fin sold for outboard motors and adabt it for swimming and it would cost less that any of these products and be just as portable and usefull.


Wow! $1200 for a fin! Not being a free diver I wouldn't like to comment on its suitability for that but for recreational diving I can't see a situation where I'd choose to have my legs manacled rigidly together. Perhaps I've missed the whole point of the fin?

The video would have been much better if they had shown a comparison between the device and comparable fins in a swimming pool. In the sea I would have liked to see the demonstrator scooting along at a ridiculous speed with possibly even a little attempt at a breach.

I hope all our comments prove wrong and within a year all swimmers have one but I will have to see more uses before this swimmer plunks down $1200 (even $200) for one.

Dr. Veritas
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