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Ergonomics is a term used in many man/machine interface devices. It is defined as an item “designed to minimize physical effort and discomfort, and hence maximize efficiency.”  That is the basis for the design of DEFIANT XT.   Our goal was to design an overall fit that can best propel a human through a medium (water) as efficiently as possible.   The fact is, regardless of how you do it,  it takes a finite amount of energy to push you through the water… that is a restriction within the laws of physics.   How we choose to expend the needed energy with minimal impact to the human body is where we gain efficiency on a human level.   The human body is where we make things better! It is the ambiguous piece of the puzzle that allows us to manipulate our design to best suit the diver.


Modular design 

Defiant fins are modular in their design.  The foot pocket and stiffeners are separate from the fin base itself.  

This allows a user to swap out not only designs and colors, but the overall feel of the fin as well as switching

from barefoot to boot type foot pockets.   The Stainless steel bolts are designed to provide years of care free use.

Bi-Directional rigidity

Often fins are built with an I-beam running the length of the fin on each side. While this adds rigidity, it isn’t  very streamlined. DEFIANT, SHIFT, and APEX XT uses an arched design to gain rigidity.  

Viewed from the front, DEFIANT, SHIFT, and APEX XT makes a slight

U shape. If you were to place it on a table, the outer edges lift from the

table about 1 ¼ inches.   From a physics point of view, this has the same

effect as having a 1 ¼ inch beam down the side,  but fluid dynamics aren’t 

compromised.  Better streamlining for better performance and no 

clumpy I-beams. The crescent shape of the fin compliments the design 

to channel water and provide better control.  



Variable Rate Stiffeners 

Durometer is a measurement of how hard rubber, polyurethane and other pliable products are.  Variable rate stiffeners

use different durometers of material and/or thickness of product to allow the user to adjust how flexible the working

portion of the fin is.  This allows the diver to customize the fin for his/her strength, swim style and comfort.  The

stiffeners are on the top of the fin and held in place by 12 stainless steel bolts.   The rear bolts near the foot pocket

hold the stiffener firmly in place while the front four (two on each side) are designed to tighten on themselves, leaving

enough play in the stiffener for movement.  The stiffener itself can move forward on the return stroke.   This 

relieves tension in the fin for easier movement on the most inefficient portion of the kick cycle.  While kicking

downward on the power stroke, the stiffeners engage.  Because the stiffeners are on top of the fin and secured at

both ends, it length must increase in order for the fin to bend.   This is what allows us to make a relatively flexible

part make a significant difference in performance.  The stiffener has to actually stretch.  

It makes perfect sense that a fin creating a specific amount of resistance will work for one person and not for another.

Additionally, as divers become stronger in their kick they can increase their fins rigidity and maintain a perfect balance

of strength, thrust, and stamina.  The same is true for those with leg injuries.  DEFIANT, SHIFT, and APEX XT stiffeners

were designed with this logic in mind.


DEFIANT, SHIFT, and APEX XT is a shorter design than many fins.   The length has been carefully determined based on the limitations of the human body.



    The shorter length of the fin decreases the amount of leverage working against the body.  To illustrate consider holding five pounds in your hand at arms length. Hanging             the same weight on the end of a broom handle would create a lot more strain.   The weight hasn’t changed, just  the leverage working against the body. DEFIANT, SHIFT, and     APEX XT use the same principle

    Length & the law of diminishing returns

    The advantage of a long fin is greater throw.   However, it puts the divers fin farther out of the slip stream that he/she creates.   It is the same effect as air brakes on an                 airplane or even sticking your hand out of the window of  a moving car.   While there is some gain in the additional length of the kick, the law of diminishing returns is

    in play.  The following simplified graphic show this.   In the graphic the two divers are identical with the exception of the length of the fin.   The dark red indicates the

    area that is out of the slip stream, or the additional resistance area. The diver on top with the longer fins has greater additional resistance.  The amount of additional

    resistance is indicated in the bright red.   The diver on bottom has less additional resistance.   The amount less is indicated in green.



DEFIANT, SHIFT, and APEX XT fins are slightly wider than many fins.  This width provides additional surface area of the fin at a position that uses leverage in the favor of the diver.   

Power Transfer


One of the best ways to get more power from a fin is to direct the energy into the working area of the fin.   DEFIANT, SHIFT, and APEX XT stiffer durometer foot pocket minimizes the amount of the divers energy stretching the pocket while still maintaining a comfortable feel.   A more rigid power transfer plate under the foot then transfers energy to the front working portion of the fin.




Will the shorter length keep me from going as fast?


First let’s look at speed types.   There is a difference between quick and fast.  To illustrate, consider a twelve speed bicycle starting out on a hill.  If you were in first gear it would be very easy to pedal (think kick) and you would achieve that gears max speed in a short amount of time.  That defines quick.   If you started in 12th gear it would be very difficult to pedal (think kick) and it would take a long time to get up to that gears max speed.   However,  that gears max speed is far faster as rated by miles per hour. That defines fast.   This is similar to the fins shorter length (1st gear) vs other fins longer length (12th gear).   However, the difference in speeds (gears) is not 1st vs 12th.   Its is about 1st vs 1.25-1.5.  If two people were to race a bicycle up a hill in this configuration, the rider in 1st gear would have an easier time pedaling (think kick) against the resistance of the hill (water) and the rider on a 1.5 speed bike would have a harder time pedaling against the resistance of the hill (water).  For the two riders to tie, the rider in 1st gear would have to pedal more times,  but each rotation would require less effort.  This is the human element.   Getting the gear or fin length right allows a diver to kick easier without losing top speed.   Because the ratio of the DEFIANT XT is close to longer fins,  and because a diver can easily increase his kicking cadence,  the answer to this question is no.   It also means that a diver will feel less tired going over the same distance at the same speed… just like on a bicycle. Indigo’s comparative speed test results support this.


Do they work well with other kicks,  like frog kick


DEFIANT, SHIFT, and APEX XT works exceptionally well with other kicks,  like the frog and dolphin kick.   It’s slightly shorter length provides outstanding agility that you wont find in other fins. 

Power Xfer
Anchor 1

Fin Design

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