How do Mermaid Tails Work?

Swimming in a mermaid tail is a lot of fun. But have you ever wondered how these tails actually work? I certainly have, so I did a bit of research on the mechanism behind the way the tails help you move underwater. Here is what I found.

Mermaid tails work by using the same principles that sports monofins and animal parts like dolphin flukes use as well: The monofin can create a resistance against the water because of its flat shape. So, when their user moves the tail up and down this propels them forward through the water.

There are two parts of a mermaid tail: the monofin and the fabric (or silicone) tail. The monofin does most of the work and allows you to actually move. So let’s have a closer look.

What does a monofin do?

A mermaid monofin (Mahina Merfin).

There are many aspects involved in how mermaid tails work. For example it makes a difference if you swim in a lightweight fabric tail or a heavy silicone tail. But in this article I will only look at the most important part of every mermaid tail: the monofin.

It is the monofin that actually helps you propel through the water when you swim in a mermaid tail. Because of that, mermaid swimming is at it’s core the same as monofin swimming.

The monofin consists of a flat surface area, that is often shaped like a fish fin or dolphin fluke, and foot pockets or other kinds of foot-holds. Instead of using one fin for each foot, like bifins do, when using a monofin both feet go into the monofin together.

This not only makes you look like a mermaid or a merman, but it also helps you propel through the water much faster than with bifins because of the bigger surface area, more streamlined shape and the fact that you can put more power into your kicks if you use two feet.

Monofins in general work very similar to whale and dolphin flukes. Whales and dolphins also use equal force on both sides of their body to do the typical dolphin kick which helps them propel quickly through the water.

A monofin works similar to a whale or dolphin fluke.

Dolphins are actually the fastest mammal in the water. They can achieve top speeds of 64 km/h. With a monofin, a human can get half as fast as dolphins (30km/h), which is incredible if you consider that we only reach swimming speed of about 9 km/h on our own!

On the following pictures you can see how exactly the monofin works in the water. The swimming technique you need to use when swimming with a monofin is the dolphin kick which features upstrokes and downstrokes.

monofin downstroke
Monofin downstroke.

During the downstrokes, you push the blade of the monofin down. Because of the big surface of the monofin, this creates a resistance, which propels you forward.

monofin upstroke
Monofin upstroke.

During the upstrokes the same thing happens, just that now the water on the top of the monofin is pushed away.

It is only through the force that is created by the upstroke and downstroke that you are pushed forward through the water. In this regard the monofin actually has alot in common with wings, which do the same thing in the air.

If you are interested in all the physical details behind monofin swimming check out this great post by bewaterfreediving.

What is special about the way mermaid monofins work?

Monofins are mostly used in freediving, finswimming and mermaiding.

Freediving often happens in the ocean where people dive without diving gear. Some freedivers do it to experience the underwater world, others try to to reach records in deep diving (this can be very dangerous). So monofins for freediving are very sturdy, so that you can use them safely in the ocean.

Finswimming mostly involves competitive swimming in different kinds of fins. Since monofins are the fastest fins available, they are very popular in this sport and are mainly used for speed.

And then there is of course mermaiding, which is not so much about speed and power alone but more about having fun in the fins as well as the aesthetics of the look.

So, as you can see, there are a lot of different use cases for monofins, which means that there are also a lot of different models for all kinds of needs available.

What is special about the mermaid monofins is first and foremost their look. They work very similar to the sporty monofins, as they are also require the dolphin kick technique and work by creating a resistance against the water, that propels you forward.

But the often are not designed to be as fast as most sport monofins but instead the mermaid look is prioritized. Thus, besides their colorful design, they often are softer and smaller, and thus cannot create quite as much power as the sports monofins.

So, you can say that mermaid monofins are generally a bit slower and less powerful than most sport monofins. There are however a few models that have very similar qualities to the fastest fins whilst also looking mermaidy (e.g. the Mahina Merfin).

How do small monofins work?

Smaller fins cut the water better, so it is easier to do spins and flips in them. They are also better for ab workouts, because you need to kick more often in them than with a long fin, that elongates your movements.

How do big monofins work?

The bigger the fin, the more water you move. Longer fins make it easier to glide though the water more effortlessly by elongating the movement of your body. This happens because the water rolls under the fin and can thus give you more power.

If you swim in the ocean, a lot of propulsion is important because there is usually a lot of currents tides, you neeed a bigger, stiffer blade so you can feel safer and have more power

How do soft monofins work?

Swimming with a softer monofin is often a bit easier for beginners because softer fins are more flowy. Especially if the fin is also a bit longer if easily continues the wave movement of your body and you do not always have to use perfect technique (perfect dolphin kick) and can still move rather easily.

How do hard monofins work?

Swimming with harder monofins requires more energy and technique than swimming with a soft one because you have to push even harder to move a hard fin as much as a soft one. This means you need to do all the work with your body by kicking harder, which also makes it a better ab workout.

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