I'll bet some of the pink ones are extending to 6' deep. We fish from a floating dock and boats, and also swim from the dock, so they are not a problem. Fishing near them is productive as the fish seem to like to hang out under them. I have never fertilized because they seem to grow and bloom well without it. They are over 10 years old, maybe closer to 15 years old. They have spread when dug up by critters causing the tubers float around and re-root. I am good with this since we have plenty of open water. I think that they have helped control submerged plants as well. We have added them to other ponds and wetlands on our place as well as sharing with other pond owners. The only drawback for me is that the hardy water lilies are all morning bloomers.