@AndrewKSheaff: It is very, very difficult to ...

It is very, very difficult to swim fast butterfly without an effective entry kick.

The quality of the kick matters, and the timing of the kick matters just as much.

A great entry kick serves 2 key roles.

First, by kicking down, it lifts the hips up, greatly reducing drag at a time when swimmers are creating a lot during the recovery of the arms.

Less drag means more speed for less effort.

Second, the kick creates propulsion at a time when there is very little propulsion being created between arms strokes.

More propulsion, more speed.

By eliminating drag and creating propulsion, the kick quickly helps swimmers transition from a low speed position to a high speed position, which is critical for creating sustainable speed.