There is no perfect underwater kicking amplitude for all swimmers,...

The key is to help them find it.
Larger kicking amplitudes have the potential to create more propulsion, but also less drag.
And a swimmer’s individual structure also impacts these relationships.
Here’s one way I like to help swimmers figure out what works for them.
Their goal is to determine which is most comfortable for them & creates the most speed.
By using a range of amplitudes, they’re more likely to figure out what works for them.
Explore the options and find the solution that leads to the most speed.