Butterfly stroke
swimming stroke swum on the breast, with both arms moving simultaneously
Butterfly (shortened to fly) is a swimming stroke swum on the front. Both the arms and the legs are symmetric, with the arms moving symmetrically down the front of the body and then over the water, and the legs moving up and down together in a dolphin kick.
Technique
Butterfly, shortened to "fly", is a symmetric and undulating stroke. For most competitive swimmers, butterfly is the second fastest stroke, slower only than front crawl. Edward Wasserman wrote that for most competitive swimming fans, butterfly is the most exciting to watch.
During butterfly, the arms move symmetrically down the front of the body and then over the water, while the legs move up and down together in a dolphin kick. Each butterfly stroke cycle consists of two kicks and one full arm stroke, with each stroke cycle beginning when the arms enter the water in front.
Arm movement
The butterfly arm movement can be broken down into five phases: the entry and stretch, the outsweep and catch, the insweep, the upsweep, and the release and recovery.
Entry and stretch
The entry and stretch begins when the arms enter the water above the head. The arms should enter straight or with the elbows slightly bent, about shoulder-width apart, and with the thumbs pointing downward so that the hands can slice into the water.
This brief starts where responsible research should: with the source description of “Butterfly stroke” as swimming stroke swum on the breast, with both arms moving simultaneously. Everything that follows is an evidence route, not borrowed authority.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 29, 2026. The linked authority identifier is Q245249. The Library of Congress control number is sh85131210. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Butterfly stroke” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.