I've put just any kind of canna in the pond and they seem to do well. I generally plant them in dirt (without any vermiculite that floats) and put gravel on top of the pot and then sink it a foot or so in the pond. They have all grown and bloomed. I don't have any in there now for the same reason Bonnie took them out, they blow over easily because they get so tall and it is a hassle. Because I'm in the tropics, I could leave them in there all year but I got tired of cleaning up the dirt and rocks that would spill out when they fell over. I may put some more in there one day, when enough time has passed that I forget what a hassle they are
Years ago in Calif I had cannas (not specifically water cannas, just ones that were at Lowe's) in a skippy filter on a pond. They were bare root in gravel. They also did well and bloomed and ended up sending up so many pups that they filled the filter and it was a heck of job to get them out.
