Thinking Diver

Where divers think about stuff


Fins: what I wish I’d known

by Twain

I wince when I think of the money I’ve wasted on bad gear as I was learning to dive. Maybe it’s my propensity for shiny new toys, but I’d rather blame it on a communications gap between the “technical” and recreational dive worlds.

Every year dive gear manufacturers come out with new features for their regulators, wetsuits, and BCs. There’s a good business reason for this: manufacturers need to differentiate their product and get consumers to buy more each year. It’s hard to build a business around a commoditized simple item. I suspect golf is like this too.

The irony is that diving is one of the few gear-intensive sports where the best stuff is the simplest and often cheapest. By the time you get to technical diving you know this, but meanwhile you’ve wasted a fortune on recreational junk which you could have avoided had there been a nearby technical diver to ask.

So here is the first of my “I wish I’d known that” gear posts.

Fins

Fins are important. They are how you control your movement under water: forwards, backwards, and turning. (Yes, turning – your hands are for handling gear not swimming.)

I recommend two things to consider when choosing fins. One is obvious, the other maybe not.

Fins Shape – Split or Paddle?

Oh, I wish someone had pointed this out to me before I’d started buying gear.

A very popular design these days is the “split” fin. (I used a set of these for several years.)

What split fins do well: high-rpm flutter kicking. When you flutter kick, each “leaf” twists creating a propeller-like effect. This makes it quite good for fast flutter kicks and straight-line speed tests. Sounds great, right?
Split Fins
However, here’s the kicker (sorry, couldn’t resist!) — you are not high-rpm flutter kicking when scuba diving!

  • First of all, you shouldn’t be swimming hard to begin with — if you are working hard, something is wrong. Working hard will chew through your gas if you’re on open circuit or put you at risk of carbon dioxide buildup if you’re on a rebreather. If I could drift or get pulled (scooter!) the entire dive that would be just perfect.
  • Second, the kick of choice for advanced diving is not a flutter kick. Flutter kicks push water downwards to cause billows of visibility-killing silt or disturb reef life. If you flutter kicked through a wreck you would likely piss off or endanger nearby divers with clouds of silt.
  • What split fins lack: the stiffness and body you need for frog-kicking, turning and backing up.

  • Frog kicking – this is the kick used by technical divers because it pushes water behind you where it won’t stir up silt. The short, sideways motion of a frog kick does nothing if you have a fin designed to be moved vertically.
  • Turning – you pivot your body underwater by moving your fins in small vertical circles. Doing this with a split fin makes the “leaves” of the fin flutter and inhibit the sideways foot motion, accomplishing almost nothing.
  • Backing up is even worse…you are trying to pull water towards yourself but your “scoop” is functioning like a fork instead of a spoon. OK, maybe a spork. You might as well be barefoot.

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