I went swimming after work. After freaking out about it for so long, I finally got up the nerve and did it, and I am so glad I did. I managed 20 lengths in about half an hour or so (it took me a while to find the clock) which is abou double what I thought I'd manage, so I am pleased with that.

I think I'll try going at lunch time later in the week - see if it's quieter. I will certainly be making it a regular thing.