Will can swim as there are various waterways around Nottingham and swimming is how you clean off.

Charles can swim though I think its not his favorite exercise, I'm not sure what is.

William can swim as I think he grew up in an area with more water than Arizona. I've never been clear on where the Evans' family lived before Arizona but it was somewhere east and I think Dan mentions being a sharpshooter for a Massachusetts' company.

Sameth can also swim as water is important in the Old Kingdom, knowing your way in and around it can save you from the Dead. Though he does have some issues with drowning, thanks canon.

I think Moist can as it seems like a useful skill to learn but I can't see it as being easy to learn in Uberwald.

Jane, I feel like she learned to swim when she was a girl against her mother's wishes but hasn't swum in a long time. Its not ladylike.

Demeter can swim as well, because goddess, she can do whatever she wants to if she puts her mind to it.

Tumnus, I think can swim but doesn't do it that often, it makes his fur dry in weird ways.

The Pirate King can definitely swim and looks good doing it.