I used to go swimming on a regular basis. Changing facilities were such that I didn’t have to worry about changing in front of people. It took me a long time before I felt comfortable enough to swap from a tri-suit which covered up most of my body and was unisex enough that I could wear it pre-surgery and post-surgery. Eventually I reached the point where I felt able to start swimming wearing a swimsuit.
However, I only do that during the early morning swim sessions. Even now, 2 years after surgery I would not dream of going swimming to any session where there are parents with youngsters because I still worry about how people would react if they realised I had a trans background.
I like the point you make about cis people not having to defend their very existence. There are very few people in the world who have to justify the fact that they exist and only want to go about their lives, that they just want to deal with all the stuff that life throws at people, in exactly the same way that cis people do.