@foonfoon65 Welcome to Mayo Connect, where patients and caregivers meet to support one another and share our experiences.
When you say, "I was told I may have gotten MAC from swimming in a public pool..." who told you that?
As a new member, I am thinking you may be new on your MAC journey, and right now you have a lot of unanswered questions. Here is what we know about MAC bacteria - it is everywhere, in the air, soil and water. The only way to completely avoid exposure is to live in a bubble. So, what we need to do is to decide where our most high risk exposure is and minimize or avoid it, then get on with our lives.

That said, the mist-laden air above indoor pools and hot tubs can have a high concentration of MAC (and other) bacteria, and for most of us should be avoided. On the other hand, outdoor swimming pools, where the moisture easily drifts away and the air is well-diluted by the atmosphere, the risk is substantially lower. And even lower yet for a salt water pool. Depending on one's risk tolerance, that may mean feeling same in outdoor pools.
My own take, after almost 5 years with MAC & Bronchiectasis - I avoid indoor pools completely - which is awful in winter when my kids and grands want us to swim together at the Y. I have completely given up hot tub use. But I regularly swim and exercise in outdoor pools, freshwater lakes and the ocean. This feels safe enough to me, and so far I have not been reinfected (off antibiotics for 4 years.) However, if I get an exacerbation - cold, bronchitis, etc - such as the one I am fighting off now - I stay away from the pool until I am well. But I will still go to the ocean near us, because NTM is scarce to non-existent in salt water.

I am curious whether the doctor who told you a swimming pool was safe specified outdoor? Are they a pulmonologist familiar with MAC?
Sue