ELI5 Swimming - why are there exactly 4 strokes?

Why are there exactly four strokes in swimming? Why are the Native Americans credited with the invention of Front Crawl and why is it also called the Australian Crawl? How did Butterfly come about as a variation of breaststroke? When was the dolphin kick invented? ... we explain like I'm five To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]