Thankfully I live in a country, where wearing a swimsuit is possible perhaps for a few days in a year. So there is not even a temptation for me to wear it.
There is of course the public swimming halls, but I cannot imagine of going there, as you would be in close quarter with other women. Everybody else naked and you wearing the swimsuit, for which you get a permission to wear on all times, even at sauna.
It just would feel strange, even when I know that many transwomen do go to the swimming halls.