Here's an easier way to lift up heavy lilies to repot them or simply move them closer to the surface.
My pond is all one depth. My solution is to clean the pond in the spring. I pump out about 1/2 to 2/3 of the water, that makes it easy to find all the pots and they are easier (but still not EASY) to lift out. I repot, put back, then gradually add more water as the pads grow taller. So basically instead of lowering and raising the lilies, I'm lowering and raising the water level. Of course, if you have marginal plants that you can't easily move around, they risk getting too dried out while all this silliness goes on. Or if you have lots of fish, they might not have enough water to stay happy.
Sometimes I do the same thing in the fall to make it easier to clean up the lilies for winter.