japanese water iris

do these just grow in shallow water? I have a pond but the shallowest is 1 foot
Is that too deep?

also are they hardy over the winter and come back?

I'm not sure what you're referring to as Japanese water iris. If you mean Japanese iris, they are hardy and do come back. If your shallowest area is 1 foot, it would be best to plant them in a container, and set it on a little shelf. Take the container up in the fall, and sink it in the ground to overwinter. Or you could plant them on the side of the pond, so they only get a few inches of water. If you are in Z7 or above they will overwinter in water. If in Z6 or below they don't as they can't take the water freezing over the crown.

Japanese irises aren't really water irises, although they do like a lot of water. A lot of people think they are water irises as they've seen the pictures of them in water in Japan, but in truth in Japan, they just flood the iris beds for picture taking, and the irises are not actually grown that way.

Please give one a try, you'll love them.