This was a great preparation book for my 4 year old's first swimming lessons. He's always very tentative about new things and has never felt good about the water, so we approached the swimming class with trepidation on all parts. This book narrates all the things you might experience in a swimming lesson, from kicking and paddling to getting your face wet. Like you'd expect from DK books, there's a lot of new vocabulary listed so there's a picture word glossary at the very end. 
 Probably my favorite thing about this book is that it's a father/son combo taking the swimming lesson, and I still find it hard to find a lot of good books featuring fathers doing everyday activities. This worked out really well for us, since my son was taking the lesson with his dad. Very recommended for any budding swimmers.