The Freediving Big Question: Which Blade and How Stiff?

20141107 WaterMaarq Adelaide Stage-A Freediving-13This is the question that rolls most around the pool deck and the shoreline amongst my diving buddies.

Some swear by fibreglass, others by plastic, and like a self-fulfilling prophecy, well there’s some who will say you’re wasting your time with anything other than carbon.

Fins and Bicycling?

I digress. In the finning circles, oh no, puns already, one of the poor finning techniques referred to is “bicycling”. This is where the finning action looks like the legs are pedalling rather than finning.

I digress further… Lance Armstrong. Who? No he doesn’t freedive, well not yet, but he might do pretty good actually. And I won’t get into that whole cheat/drug discussion either.

What he did for cycling in terms of pedalling proficiency, or cadence, was majorly disrupt the common thinking of how to pedal a bike fast, for a long way.

Let’s hear from his former coach Chris Carmichael about that technique for a minute:


What Chris talks about is breaking a hill climb into smaller pieces by having a higher rate of pedalling (cadence) and using less effort. This is like finning. We want less effort, breaking the swim into smaller pieces without sacrificing propulsion.

I’ll get back to finning in a second.

Power = ?

In cycling terms Power = Force x Speed.

This means if I have strong legs and pedal quickly (high cadence – 110/120RPM) I should go super fast (=Lance!)

If I have strong legs and pedal slowly using a big hard gear I can go as fast as Lance maybe, but I will use much more force at a lower cadence (Lance’s old rival: Jan Ullrich used to pedal at about 70/80RPM when climbing compared to lance 100+ RPM)

Let’s take a look at Lance and Jan racing. If it’s a blue or yellow jersey, it’s probably Lance, if it’s green, pink or white it’ll be Jan.

In this clip you’ll see at various stages both racing up the hill side by side. Observe their pedalling stroke, Lance is fast, Jan is slower. It means Lance uses less effort in legs, but more of his fitness. Jan is using more strength than body fitness to go the same pace. Which one do you think would wear out faster? Relying on strength or fitness? Who could accelerate faster and be more dynamic?

If I’m a whippet that weighs 50kg, I can’t push a big hard gear like Jan, it must be an easier one because I don’t have the strength or force. But I have every chance to spin like crazy at 140RPM and go the same pace like Lance.

So why am I going into this?


Putting fins on is a bit like the old Power = Force x Speed equation.

If I have super strong legs I can kick a stiff hard fin and propel myself, probably using a lower frequency or cadence (fin strokes per minute for example).


Let’s take a look at Annelize Muller using plastic long freediving fins during the dynamic swim in the pool.

From 0’27” onwards, notice how the stroke is relatively slow? Plastic fins are quite stiff and require good strength to push them through the water swiftly.

Now let’s check our Burni Brewis who is using shorter plastic/rubber fins during the dynamic swim. Again, see from around 0’27”.

Slightly quicker stroke, less effort because the fins are shorter and require less strength to fin, but less propulsion.

Finally, here’s Jenny McSwimmyfish performing a dynamic in long carbon blade fins.

You’ll notice in this clip that the fin stroke is relatively slow but the blade tracks very nicely on the upward/downward plane. It appears from the surface that there is some hip roll occurring side to side, this may indicate the fin is too stiff and a softer blade or stronger core/legs could be introduced to overcome this.

So, in summary, if I’m a whippet 50kg lightweight freediver with legs like twigs, I’ll want a very flexible/soft fin and to kick it in a faster, less aggressive manner.

If I’m in the average range, I can kick a moderately stiff fin (medium / 25 stiffness), in a range of frequency (cadence we’ll call it) and propel myself comfortably.

20141004 B4S Port Melbourne-10

How to Test Which Fin Blade is Best?

Establish your baseline distance and standard fins that you like, let’s call it a 25m length in a pool.

Strap on your fins and keep all other things standardised throughout, e.g. your breathing preparation sequence, final breath, wetsuit, weighting, eyewear, the pool you use.

Remember, always, always freedive with a buddy who is with you on each swim.

Swim a 25m dynamic underwater and time your length using the standardised fins. Use your comfortable cadence in finning. Count your finning strokes for the length and time the lap. For ease of test, fin from the very beginning, don’t glide.

Maybe do it three times to establish an baseline from the averages. You want to establish a general idea, but with some level of confidence.

Grab your other fins and do one or two swims with the same protocol. Record your results:

  • Time to complete the lap
  • Number of strokes
  • Record your perception of how you thought the fins performed, e.g. slower than your regular ones, harder/easier, more force/less, smoother/sloppier.

If your buddy happens to have the same shoe size, that’s a bonus, you can get an even better sense of  what suits you and why when you both run the test.

What Should I be Looking For?

20141024 Stage A Freediving Port Melbourne-12At the end of your trial, you want to understand which fin was fastest, which felt the best, and which maintained a smooth and swift technique. Ultimately the fin which got you to the end in the best time with the least amount of strokes and kept you freshest is best for you.

Personally I’ve used standard plastic fins like Cressi Gara Modular which I found too stiff and unresponsive, like boards. Probably okay if you have legs like a weightlifter. My preference is the Pelagic super soft blue fins. These were chosen to be the standard fins available for hire during courses, because of their durability, blade softness and performance. Plus the ability to suit a range of freedivers.

In the kit bag, there’s also been the Fins4U carbon blades with medium stiffness which for my build and style suited the best thus far. A range of full foot rubber snorkel fins from Tusa are pretty much my favourite for shallow work around piers, jetties and rocks.

And recently a pair of custom carbon fins (soft blade) have been put through their paces in depth, pool and rough backbench conditions. Ultimately the blade is too soft, but they will suit someone with a lighter build much better. The medium stiffness version are in transit!

Edit 14_8_2015

We think so highly of the Pelagic Spirit Blue fins that they are fin offered for hire during training and courses. They can’t be beaten for value, resilience and performance for their price. You can also now purchase them in the shop.


How About You?

So, what’s best for you?

To start, I’d recommend the softest plastic long fin you can find. Softer is better, you can always get stronger or develop your finning technique with a shorter or softer blade. Start with a stiff fin and you’ll be finning in big ugly squares, like a bad cyclist.

Work your way up over time, get to know foot pockets, blade performance, your finning style and the use of your fin. Goodness knows, maybe next you’ll be strapping on a monofin!

Please let us know your experience and whether this approach may work for you?

20141104 Bridgewater Bay with Carl-2

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