If you want to foster a swimming routine as an adult, it would help, of course, to have once been a high schooler bouncing from one meet to another around the county. But don’t worry, it’s possible to adopt the sport with no prior training. You don’t need to be fast, or even good, to thrive in the pool. You just need a little guidance to get you started — and maybe a few words of encouragement from someone who is fast.