Cath,
Yes, they have showers.
In summer, they're often cold, but it feels good.
Many have hot water, or at least "very warm" but it's not like at home.
The showers are almost always private or at least semi private. For instance, in the girls' locker, the shower stalls may not have doors, but they have walls between each shower. Believe me, nobody is interested in googling you... everyone wants to get their shower and get out.
The showers are small. You must take a ziplock baggie to put your passport and money in and TAKE IT INTO THE SHOWER WITH YOU. Never leave it with anyone else or in your bags. There are threads about this that you can find on here.
Does that help?