"They can be placed in a pot with drain holes in a very large fish bowl, and in some circumstances the pot may not even be necessary. In an aquarium, the height of the plant will have to be taken in consideration. You will need to get the plant to a level where the roots have access to water, but the top of the plant will be growing out of the water. The exact height where it will need to be placed will vary, though I would not recommend putting more than ¼ to 1/3 of the stem underwater. In short tank, Cyprus can be planted directly into a good substrate. In a taller tank the plant may need to be raised in some way, usually by planting in a pot the same way I recommended for fish bowls. In tall tanks, using large glass vases may work. These are readily available and, as long as the top of the vase is under the surface of the water, the plant will be fine without drain holes to let water into the root area. The aquarium itself can also be designed to grow emergent plants. I have a very tall 30-gallon tank in which I used pieces of glass and aquarium sealant to divide the back corners of the tank. This created two separate areas, which I filled with substrate and gravel and used as planters. More natural-looking arrangements can also be designed.” quoted from tfh issue nov 2010
i have see people use trellis and raft kits for ripariums to grow plants out of thw water.