Update....FWIW my experience has been that there is more to planting bareroot marginals than just sticking them in the bottom and walking away. Wave action, wind, curious critters, etc and before you know it you have a few floaters and then a few more and then a few more...Everyday I walk the pond and fish out 3 or 4 floaters and replant. During replant, I have been placing a few small rocks around the base of the plant and have had no repeat offenders yet.