Yeah, it may either be a regional thing or I just never paid much attention to it. The one pond in my neighborhood is completely ringed with cattails, mostly the broadleaf variety. They don't grow any deeper than 18" and that is water height at spring flooding. Soils vary greatly in the region but we do have a lot of our famous Virginia Red Clay. Now that I think about it, there is a larger pond near by that does have some cattails growing at a fairly deep depth. Next time I am there I'll have to see just how deep of water they're growing in.