shinfin fins give you smooth streamlined thrust throughout your kick. You feel the smooth force during your down kick, your up kick and the transitions between kicks. They work best for freestyle, backstroke and butterfly. You need smooth forces throughout your kicks to optimise your stroke efficiency.
Because regular foot fins are on your feet, when you swim with them you can feel the thrust pulsing during each kick. The forces build up towards the end of each down kick. You can hear the changing sound as the water surges past your ears. So foot flippers give you a fluctuating thrust throughout your kick. Many swimmers find it difficult to get a smooth thrust from their kick, even without fins. But foot flippers make this problem even worse, increasing the surging of the propulsion. They do not give continuous thrust throughout each kick, as is needed for best body streamlining and stroke efficiency. So foot flippers alter your whole stroke.
shinfin fins give you smooth thrust throughout each stroke because they attach to your legs . They lift your legs horizontal. So you can kick from your hips with only a little knee-bend. They also flex smoothly towards and away from your legs during your kick cycle. This keeps your kick forces as smooth as possible throughout your kick. And that helps you pull smoothly with your arms too. Together, this gives you a continuous streamlined thrust during each stroke for more efficient swimming. You hear a smooth and steady sound as the water flows past your ears to tell you how consistent your speed is.
shinfin fins teach you a streamlined thrust throughout your kick, even if you don’t yet do that. With practice, your body will remember their continuous streamlined thrust, even when you go back to swimming without fins. So they improve your normal swimming stroke too.
Now you can have fins for extra propulsion and have a streamlined thrust throughout kick!