Melissa, I'd advise you to get a book on water gardens, before you start this project (if you haven't already). When we moved into this house that already has a water garden, I bought a book called "Water Gardening for the South" by Teri Dunn. It was a huge help to me, getting started with water gardening and I still use it after 8 years.
I believe Teri Dunn has a whole series of these "Can't miss" books for all areas of the country.
Here's a link to the one for the Northwest, used on Amazon for under $2!
https://www.amazon.com/dp/1591861527/