I'm pre-op, full-time and swim regularly. My local pool has mixed gender changing cubicles, so changing is not an issue, but the showers are open-plan.
I had been using the ladies showers, while remaining in my costume, but last time, another lady did strip entirely, and I felt VERY awkward! I have no idea if she clocked me and didn't care, or she didn't realise. I've decided I'll shower at home after from now on, not ideal, but I'll certainly feel more comfortable.