This is even better. It's a little extra work up front, but after that it's much simpler.

Turn off the built-in diffuse.

Combine the Refract with a Diffuse node using a Blender. The Blending value will determine the correct proportions between the two nodes automatically. Arranged as I've done, the lower that number, the less clear the water is.

---

Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)