what are the rules of butterfly style?

Former Member
Former Member
In the near future would like to participate in IM 100 and 200y however, my butterfly is my slowest style I can swim about 5 sec faster (per 25y) doing dolphin like movments (kicks and whole body ondulation) under water with occasional surfacing to breath Surfacing slows me down so before i continue my underwater butterfly/dolphin i take one breastroke kick and hands stroke What are the rules defining minimum requirements for butterfly style? Do i have to move my hands forward over the water? Moving arms over the water, as in classic butterfly, seems to aggravate my shoulder muscles/joint (impingment?) so i am trying to limit or avoid this kind of movement Are there any other alternatives to swim healthy shoulder friendly butterfly? thanks