Cape, the water fringe/floating heart I found grows the best when tucked in between rocks on the edge of a pond, or in a stream, tucked in the edge rocks. What I took out for the others I only had to move a couple of flat rocks on the side edge, and those roots were literally holding that rock on the slant. The roots were THICK, too.
Another thing I found today, the water parsley wants to come out of the bog and grow in the ground, and some penny wart WAS growing in the ground. Not sure how that got there, the PW that is, thinking I must have pulled some out, left the pieces on the ground, and it grew. Very strange. So, beware, don't let parsley, water clover (yep, it was doing it, too) or penny wart get out of your ponds, unless you WANT them out there. I'm going to do a massive thinning out this weekend. It's just way too thick. Problem is that I have to be super careful, make sure there aren't some "good" plants in and amongst the clover and parsley. It doesn't take long to pull it, but thinking the roots are down there just going to explode again soon. We shall see ...