When a swimmer is learning the Butterfly stroke, making a wave movement must be done.

There is more than one reason for it.

One reason is to powerfully kick in a waving or fanning motion and another is to have good hydrodynamics with the least resistance possible.

If a swimmer doesn’t get it sometimes an unusual parallel or clear analogy helps. I’ve used roller coaster as a good parallel.

The reason to make a wave is so your whole body follows the same path through the water. When you do that, you create the smallest possible hole through the water. The least resistance. The back follows the front to do this.

When the front of the coaster is at the top of a curve, the remaining cars are behind. The back-end cars will eventually take the exact same path as the front. At any one moment, each segment is doing something different, but each will bend up and down in its own time, snaking perfectly.

With this analogy, you can discuss the front of the stroke, the middle of the stroke, and the flow of the legs at the end clearly.

Each segment follows the path along its rail, performing the exact same motion as the lead, just like a Butterfly swimmer gracefully curving along the surface.

Using a clear analogy is helpful and finding a new one is memorable.