I am a master swimmer for 4 decades and use female locker rooms in the both states I live in an traveling frequently I have been to so many often for my lap swimming I can't recall them all. So in some locker rooms female nudity is not big deal. However, there are ways one can change into your swim suit, shower and get dressed without out being naked. I do it all the time. Women will also come in dressed to swim and leave afterwards without taking a shower wanting to go home and do that. I do that in Hawaii all the time..  I doubt that anyone transgender is going to take an all out shower with the ladies if they still have male parts.. The last thing trangenders want is any public attention, why would they when they know how people feel about them.