Start with planting the water lily in a small container that will be placed into a pond or tub.
Choose a 12- to 20-inch diameter container that is 8-10 inches deep and cover the drainage hole with mesh or burlap to prevent the soil from escaping. The plant grows to the size of the container, so if you are working with a small tub instead of a pond, choose a smaller pot.
Fill the pot two-thirds of the way with typical garden soil or soil made for aquatic gardening, not lightweight potting mixes containing perlite, vermiculite, or peat. You want it to be heavy. Place the rhizome against the side of the pot, with the growing tip pointing upward at about 45 degrees and toward the center of the pot. Cover all except the tip with soil and add a layer of small rocks or pea gravel to keep the soil in place.
Lower the planted pot into the pond or tub at an angle to allow air to escape. Set the base of the pot 12-16 inches deep. As they grow, the leaves will float to the surface. If your plant has leaves already developing, begin by placing the container so that the leaves are 6-8 inches deep. After several days, the leaves should reach the surface, then lower the plant to its final depth of 12-16 inches.
