My kids both swam competitvely. My youngest learned the butterfly by watching his older brother and started at 5 but my wife and I encouraged them to play a different sport each season. They both did swimming basketball lacrosse and football.

This idea of focusing on a single sport started with soccer as Americans needed to field a better team narionally. There are pros and cons I guess but IMO multi-sport is the way to go at least until hs. Kids who play 1 sport 24-7 often burn out. Plus there is emerging evidence that focusing on a single sport may lead to asymmetrical muscle development and more injuries.

My oldest just started hs. He eventually got tired of swimming and realized while he is tall he's not going to be 6-6 so dropped basketball and is now focusing on lacrosse and football. He's also thrilled I no longer coach him. Lol.