I just got a bunch of water lilies from Graham's friend (thanks!), but don't yet have a pond. I know I can winter them in the basement, but have just had it suggested to bury them in the soil outside. I like the simpler option of burying them outside, bit wanted to know if anyone has experience with this.
Your lilies will need to be kept from freezing. If the rhizomes freeze, they will desiccate and you will loose them. Keep them in a frost free environment where they will be dormant for the winter. One solution would be to plant them into a bucket or similar with enough soil in the bottom, then sufficient water over the crown of the plant, locate them where the temperature is ideally around 5C. Keep a check that it does not dry out overwinter then transfer to a pond or outdoor feature when the ice has thawed in the spring.
I cut them back and throw them in with my fish in the fish tank. They actually bloom earlier for me that way.