in 1935, Jack Sieg a swimmer also from the University of Iowa developed a kick technique involving swimming on his side and beating his legs in unison, similar to a fish tail, and then modified the technique afterward to swim it face down. He called this style Dolphin fishtail kick .
John Arthur Stephens
Dr Philip Mcallister -claimed to have invented the stroke almost 8 years before David Armbruster.
there is only a short window for breathing in the butterfly. If this window is missed, swimming becomes very difficult. Optimally, a butterfly swimmer synchronizes the taking of breaths with the undulation of the body to simplify the breathing process; doing this well requires some attention to butterfly stroke technique.
Normally, a breath is taken every other stroke. This can be sustained over long distances. Often, breathing every stroke slows the swimmer down.
Other intervals of breathing practiced by elite swimmers include the "two up, one down" approach in which the swimmer breathes for two successive strokes and then keeps their head in the water on the next stroke, which is easier on the lungs
Swimming butterfly is difficult if the core is not utilized, and correct timing and body movement makes swimming the butterfly much easier. The body moves in a wave-like fashion, controlled by the core, and as the chest is pressed down, the hips go up, and the posterior breaks the water surface and transfers into a fluid kick.
During the push phase the chest goes up and the hips are at their lowest position. In this style, the second pulse in the cycle is stronger than the first pulse, as the second pulse is more in flow with the body movement.
Although butterfly is very compatible with diving, the resulting reduction in wave drag does not lead to an overall reduction of drag. In the modern style of the Butterfly stroke one does only little vertical movement of the body.
Butterfly uses the regular start for swimming. After the start a gliding phase follows under water, followed by dolphin kicks swim under water. Swimming under water reduces the drag from breaking the surface and is very economical. Rules allow for 15 m of underwater swimming, before the head must break the surface, and regular swimming begins .
The second hand leaves the wall to be moved to the front over water. It is commonly referred to as an "over/under turn or an "open turn
Then the swimmer pushes off the wall, keeping a streamline position with the hands to the front. Similar to the start, the swimmer is allowed to swim 15m underwater before the head must break the surface. Most swimmers dolphin kick after an initial gliding phase.