This isn't applicable to most, but swimming. The majority of people (as far as I know) get taught to swim as kids, but if you're in the self taught camp like me

This isn't applicable to most, but swimming. The majority of people (as far as I know) get taught to swim as kids, but if you're in the self taught camp like me, the difference is night and day. I took about two weeks worth of swimming lessons with a private instructor, but you can see visible improvement way faster. Whereas previously I was careful not to swim in deep water, I now regularly go swimming and enjoy it immensely. The core idea is twofold, to overcome any fears you may have, and to fix your technique. The two feed back into one another in a positive feedback loop — the more comfortable you become, the more you can focus on your technique, and the better your technique, the more comfortable you are in water. For anyone who doesn't feel at home in water, I highly recommend it.