Thursday, November 30, 2023
FreedivingSebak Freediving Monofin

Sebak Freediving Monofin


Sebak Fins has joined in the race to design the perfect monofin, the Holy Grail for some of us wet people. Not satisfied with stock finswimming monofins, the company teamed up with the Finnish freediving team to develop a dedicated fin for freedivers.

Topi Lintukangas from Team Finland dove to 51m with a prototype Sebak freediving fin at the 2001 World Championships in Ibiza. His fibreglass fin was extra long, with a super soft trailing edge, plastic rails and, most striking of all, modified Omer bi-fin footpockets.?? It was the coolest thing there.

My Sebak freediving monofin came in a huge blue nylon fin bag and got me excited as soon as I took it out. It had definite sex appeal???clear, white fibreglass, black rails, a personalized sticker with my name and a Canadian flag on it???I felt like a NASCAR driver about to test a new speed machine.

Sebak has bonded the Omer footpocket in a special way. The tongue of the blade is pre-bent, angled so that when the freediver’s feet are relaxed, the blade is streamlined in line with his body???a great thing for gliding between strokes and the sinking phase of a dive.?? The fin blade is actually a few centimetres shorter than most other fins. It was surprisingly stiff for a fibreglass fin, as much or even more than my Mat-Mas carbon KSP-10.

After testing this fin over the summer, with the help of local intermediate and expert freedivers in Vancouver, it is clear that Sebak is on the right track, and that it should continue to improve this design. However, it is still a few steps away from making the ultimate fin for deep-diving.

Recreational Heaven

["Sebak Monofin" left]Two intermediate freedivers (max depth 40m), who prefer recreational diving, called the Sebak monofin the most comfortable fin they’ve ever used. Compared to other fins made by Mat-Mas, Finis, or Beier Brut, the Sebak fin is stable, easy to put on and take off, and easy to controll. The roomy Omer Millenium footpockets eliminate the constriction and numbness that plagues most monofin divers’ feet. A 5mm sock in full comfort was a pleasant change from the usual agony of jamming feet into a rubber prison.?? I also took Matt, a new freediver from Seattle, for his first day of line diving with a monofin. He dove to 25m and from the start was able to control the fin enough to make a fairly efficient descent. The Sebak fin with its stiff footpocket is forgiving enough make up for uneven foot pressure and poor stroke mechanics. You could not say this about any other fin on the market.

A Deep-Diving Fin?

The features that make this monofin so appealing to recreational divers and newcomers to the monofin hold it back from real performance.

In short: the footpocket is comfortable and warm, but it is too heavy for the fin and creates too much drag. The rails on the outer edges of the footpocket stiffen the fin too much in the centre of the blade, where a graduated flex characteristic is important. Beyond the rails, the fin becomes super-soft, which makes for a strange feel for the water when diving. The heel of the footpocket also tends to dig into the diver’s Achilles tendon on the downstroke, preventing full follow-through. The stiffness was most noticeable on the upstroke, where the fin hardly bent at all. Below 30m, the way back to the surface was laborious during the negative buoyancy phase.

For dynamic apnea, where for me the monofin should be a silent partner to the body’s undulation, this fin was conspicuous in its weight, drag, and stiffness.

Sebak’s design concept is good. The blade is well-made and the angled foot interface is an exciting innovation. But the footpockets were originally made to stablize single bi-fins from twisting and bleeding power. Using them for a monofin is overkill and prevents the fibreglass fin from working properly.

A possible solution (since the full footpocket is so good for certain things) is to make a lighter, slimmer, and tighter-fitting footpocket, shorten the rails on both sides of the fin, and cut out a piece from the heel of the footpocket to reduce contact with the Achilles tendon.

The Sebak freediving monofin is a good buy. It is the fin of choice for teaching new freedivers or bi-finners how to use a monofin. It is easy to get it to work right away, unlike a more twitchy, slippery sprint monofin that requires strong feet and legs and good technique. It is also the fin I’ve been waiting for to dive in cold water. My feet are numb from my monofins in the summer after half an hour. If comfort and enjoyment are important, choose this fin. It’s a great fin to hand to someone to try for the first time. Matt from Seattle is now a monofin convert.

In my humble opinion, Sebak can build on the angled foot interface and the full foopocket design to make a great deep-diving fin. But perhaps the Omer footpocket is not the right match for their excellent fins. ??

For more information, visit for custom designs and the dedicated freediving fins and other gear.

Peter Scott
Peter Scott
Peter Scott freedives in British Columbia, Canada. After competing in the World Championships for Canada in 2001, he has continued his exploration of the ocean through writing, art, photography, freediving, swimming, surfing, windsurfing, and travel. Visit his website at