I used to be a big time swimmer. I wasn't much for sprinting but I did a lot of distance. A week before I had the little goddess, I did a couple miles (slowly) in the pool before having a day at the spa (my other pregger friend and I decided we needed to "eat our vegetables" before lazying away the day).
When I was swimming regularly, I liked this book A LOT. It's water proof and it's bound in a way so you can use it in the pool. For me, it was for days that I needed more mental stimulation than just banging out mileage.
http://www.amazon.com/Workouts-Binde...swim+exercises
I don't swim a lot now. With the little one, it's really hard for me to squeeze a swim into my day. It's much easier for me to run (or walk with her in the baby stroller) than go to the pool. However, my fourth tri is in September and I did my 3rd tri without getting in the pool beforehand and BOY, did I regret that!!! So I'll have to get in soon no matter what.