Finning in freediving has one main aim, which is to propel you forward as far as possible, but by using as little energy as possible. Freediving fins are designed to help with this and with the correct technique you should be able to descend at around one metre per second with a relatively low amount of effort.
When you fin think of a ballet dancer pointing their feet with their legs straight. This is how your feet and legs should be positioned whilst finning. The key is to keep your legs as straight as possible both through the kick forward and the kick back with your feet staying pointed.
At the height of the kick your feet should be around shoulder width apart. Any more or less and the kick won’t be as efficient.
In terms of speed, you will want each kick cycle to take around one second, and by that I mean the kick forward and kick back for each leg. Don’t rush it though, the kick should feel relaxed and comfortable.
Correct diving technique can add huge amounts of time on to your dives. For more tips on correct diving technique check out The 10 Meter Freediver.