The Sports.SE site has been around long enough for its scope to be defined. It is clearly stated that in the [help center][1] what their scope is.

> Sports Stack Exchange is for participants, hobbyists, and fans of all
> sports and forms of competitive physical activity. We welcome
> questions of all levels. For a non-inclusive list of example topics,
> click here. 

What I'm interpreting this site to be is the focus on the **competitive** aspects of sports. Your question is highly general, and while swimming *can* be competitive, I've seen no evidence in your question that is specific towards competitive swimming. Someone who would be competitively swimming should be able to do a basic front crawl.

For the Fitness site, there is overlap, and your question would be appropriate there. To quote from [what's on topic for our site][2]:

> Physical Fitness Stack Exchange is for fitness professionals,
> athletes, trainers and enthusiasts. If you have a question about …
> 
> * improving your exercise performance or technique
> * choosing a training program
> * nutrition as it relates to exercise
> * gear and gadgets used during exercise
> * achieving physique milestones
> * injury prevention
> 
> and it is **not about**...
> 
> * the rules of a sport
> * a purchase recommendation
> * nutrition unrelated to exercise, such as food safety, nutritional needs for children, etc.
> * wellness, general health, medical advice and injuries unrelated to exercise


  [1]: http://sports.stackexchange.com/help/on-topic
  [2]: https://fitness.stackexchange.com/help/on-topic