HI Dan. Welcome to the forum!
I have a young waterlily this year too. It did seem to grow very slowly at first. I gave it a pellet of water
plant fertilizer, and once it started going, it really took off. The leaves were very small at first, but now they get about 3-4 inches across (some small ones still come up too on occasion). Be patient and it will come.
You probably won't get blooms though unless you put it in more sun. I've read that they need at least 6 hours of full sun to bloom. But... mine have not bloomed yet, so I wouldn't know that for sure.