Everything to Know About Freediving Fins

The list of things to know when it comes to freediving fins is long and can appear overwhelming at first. Freediving fins are arguably one of the most essential pieces of gear freedivers use as it's where they get their propulsion from, and the fins can dictate how easily they move through the water. Freediving is all about efficiency and conserving energy, and the best freediving fins find a delicate balance between the exertion required to kick versus the amount of thrust provided.

There is much to consider from different styles, foot pockets, materials, and more. However, when you look at each factor individually, it's easy to understand why there are so many options. This article will cover everything you need to know about freediving fins. Read on to discover the different types, styles, designs, and benefits of each.

What are Freediving Fins?

Freediving fins are a piece of equipment designed specifically for freediving that are worn on the feet and provides propulsion through the water. There are various types of freediving fins intended for different purposes and preferences.

Freediving fins are built with comfort and efficiency in mind. Unlike other fins, freediving fins are designed to propel the diver as far as possible with the least amount of energy used. This is why many, but not all, freediving fins are so long and flexible. The motion created by the extended length increases the fin's thrust, while the material's flexibility reduces the energy expenditure.

Different Types of Freediving Fins

Different types of freediving fins vary in design, construction material, and purpose. The two primary designs are bifins and monofins. Multiple styles fall under each category, but nearly all freedive fins can be placed in one of the two categories. Both bifins and monofins can be constructed from plastic, fiberglass, or carbon fiber, each of which has advantages and disadvantages.

Bifins

Bifins, as the name implies, are two separate fins, one of which is worn on each foot. The legs can move independently, and the flutter kick is the most common finning technique used with bifins. 

The fins simultaneously move to alternating sides of the body, front and back, with equal amplitude on either side and alternate back and forth. The scissoring motion created between the fins pushes the water and creates thrust through the water.

Bifins are the most common type of freediving fins as they are used in specific disciplines within competitive freediving but also have many recreational and practical applications. Having each fin move independently can increase maneuverability in the water. While this is not important for competitive freediving, it is ideal for other activities such as recreational freediving, exploration, spearfishing, and photography. 

Most bifins are the long and flowing designs people have become accustomed to, although there are shorter designs for specific purposes. There are certain types of short rubbery fins that are ideal for training and refining finning techniques. This is why they are also commonly referred to as training fins. Other short fins are used to increase maneuverability even further, usually for freediving photography, but some efficiency is sacrificed with the reduced length.

Monofins

Monofins consist of a single large fin blade in which both feet are attached in one fixed foot pocket. Rather than moving independently, the legs must move in unison in a type of “dolphin kick.”

The finning technique for monofins originates in the lower abdominals and hips and travels down the legs in a wave motion until the power is transferred to the large singular fin. It is very similar to how a dolphin swims which is why it is nicknamed the dolphin kick, or some refer to it playfully as a mermaid kick.

While monofins are not as common as bifins, many advanced and competitive freedivers prefer them as the transference of power from the body to the fin is greater. However, having both feet secured to one fin significantly reduces maneuverability. That is why monofins are generally reserved for competitions or spacious recreational dives.

Plastic Freedive Fins

Plastic freedive fins are popular due to their affordability and durability. Plastic fins are cheaper than alternative materials, making them an excellent choice for beginners. They are also highly durable and offer longevity which can be lacking in other designs.

Plastic fins are relatively cheap to produce, which is reflected in their price tag compared to fiberglass or carbon fins. Additionally, plastic is a very durable and impact-resistant material. This means they are less likely to break from wear and tear, accidental dropping, or impact.

The downside to plastic fins is that they are less efficient and are not as flexible. The stiffness options in plastic fins are relatively limited. Plastic does not return to its original shape as quickly as alternatives, reducing the “snap” freedive fins use to increase efficiency. Additionally, plastic fins can lose spring as the material ages and softens.

Fiberglass Freedive Fins

Fiberglass freedive fins are a happy medium between plastic and carbon as far as price and efficiency are concerned. Fiberglass fins tend to be less durable than plastic but slightly more resistant than carbon fins.

Fiberglass fins are popular amongst the intermediate freediver community as they are cheaper and more resistant to damage than carbon fins but more efficient than plastic fins. The layers of fiberglass and epoxy provide more flexibility and spring in the fin, which increases the transference of power.

The disadvantages of fiberglass is that it is more susceptible to damage, and they are not as efficient as carbon. Fiberglass fins should be handled with care when traveling, and you should avoid stepping on them and putting or dropping anything on top of them.

Carbon Fiber Freedive Fins

Carbon fiber freedive fins are the most efficient fins with the best balance of exertion and propulsion. Carbon fins are far more expensive than other materials and prone to damage, yet they offer the best performance.

These high-performance fins are a top choice for advanced and competitive freedivers. Carbon fins are made by layering sheets of carbon fiber along with epoxy, which gets progressively thinner towards the blade's tip. The result is an exceptionally flexible and spring-like design that increases the performance of each kick without the need for more exertion. The snap and effectiveness of the blades, along with their lightweight design, make them ideal for deep dives and extended breath holds.

Carbon fiber blades tend to be more expensive than other material options. This is why they tend to be reserved for committed freedivers and those who want to get the most out of their breath-hold. While carbon is known as a pretty robust material and can be bent nearly in half without breaking, it is exceptionally susceptible to impact damage. They will likely break if you accidentally stand on your fins or drop a hard object on them.

What are the Different Parts of Freediving Fins

The parts of freediving fins consist of the foot pocket, fin blade, and fin rails. Each component has its purpose, and various options are available depending on the diver's preference.

Foot Pockets

Foot pockets are the part of the fin which secures your feet to the fin blade. The foot pocket can either be built into the fin blade or designed to be a separate piece attached with fasteners or glue. The pockets are available in varying sizes to accommodate different users, although they tend to increase by a size range of two rather than a single size.

The most important aspect of foot pockets is the fit and comfort. The fins should fit tightly without constricting the foot to the point of it being uncomfortable. Properly fitting fins deliver the best power transference, whereas loosely fitting fins negatively affect performance. If your foot falls between the size ranges available, use the slightly large foot pocket and wear neoprene socks to make the fins fit correctly.

Integrated foot pockets tend to be used on lower-range fins that are cheaper and more appropriate for beginners. Many freedivers prefer separate foot pockets as you can choose the foot pockets that fit you best and insert whichever fin blades you like. This feature makes the fins highly customizable as many brands of fin blades are compatible with different brands of foot pockets.

Fin Blades

Fin blades are the largest part of the fin, pushing the water and creating thrust. In most cases, the fin blades are made from plastic, fiberglass, or carbon. Fin blades vary in stiffness, affecting the ease of kicking and the amount of power delivered.

Plastic fin blades are the cheapest and most durable, yet they are not as efficient as other types. Fiberglass fins are slightly more expensive, less durable, yet more efficient than plastic. Lastly, Carbon fins are the most expensive and least durable but offer the best performance.

The stiffness of fin blades generally varies from super soft, soft, medium, and hard. The stiffness should be dictated by the user's size and the fin's desired purpose to find a balance of speed and energy expenditure. The stiffer the blade, the less flexible it is, providing more snap but taking more energy to move through the water. Softer blades are highly flexible and easily moved through the water but have less snap. 

Super soft fins usually suit lighter divers weighing approximately 60kg or less. For people who weigh more, soft blades tend to be appropriate for depth and distance training and recreational diving. Medium or hard stiffness blades are generally reserved for practical applications or specific environments. For instance, spearfishermen may prefer a stiff blade so they can move through the water quickly when needed, albeit less efficient. Alternatively, those who dive in strong currents may choose a more rigid blade to overcome conditions when required.

Fin Rails

Fin rails are slightly raised pieces of rubber or plastic that run down the outer edge on each side of the fin blade. Fin rails are designed to channel the water down the fin blade, increasing propulsion and preventing the fin from needlessly straying side to side in the water.

Most fin rails tend to be the same size and thickness, although they can vary between brands. Ideally, fin rails should be high enough to channel water yet not so high that it traps a large amount of water which will take more energy to kick.

Final Thoughts

While we could discuss freediving fins for endless hours (some of us at Fluid Focus are quite the equipment nerds), we will leave it at that for now. Hopefully, you now understand the different components of freediving fins and how each can affect your comfort, performance, and bank account.

The number of options for freediving fins is seemingly neverending in today's market, and having a solid understanding of the different designs available can help immensely. Depending on how you intend to use them, be sure to pick comfortable and appropriate fins for your preferred activities.

Until next time Fluid Focus followers, happy and safe diving!

Commonly Asked Questions

Are Freediving Fins Good for Snorkeling?

Freediving fins are not ideal for snorkeling as the increased length can be hard to maneuver on the surface. Freediving fins truly shine when used underwater, where you will immediately see the benefits. 

That said, you can increase the effectiveness of using freediving fins at the surface by altering your body position. Keep your upper body and torso relatively flat on the surface but twist your lower body, so it is sideways, and both fins move side to side underwater rather than up and down at the surface.

How Long are Freediving Fins?

The length of freediving fins varies depending on the brand and intended purpose. Generally, freediving fins average about 35 inches in length, not accounting for the foot pocket. However, both shorter and longer fins are available from certain manufacturers.

Shorter freediving fins are available for training purposes which can help refine finning technique and train CO2 tolerance. Additionally, short fins may increase maneuverability in activities such as photography.

Some brands also offer “extra long” fins, which are extended compared to the average freedive fin.

Why are Freediving Fins so Long?

Freediving fins are so long because it improves the efficiency of each kick. Energy and oxygen conservation is key to freediving. Having longer fins increases the amount of water displaced with each kick without increasing the effort required to fin. This means freedivers can quickly move through the water without unnecessarily using oxygen or energy.