I checked the pond where I thought I had seen this plant, but no dice. I am pretty confident that it was there at one time, but I am not a fan of aquatic vegetation so I probably eliminated it. I remember it grew up on the bank in addition to out in the water, just as you said. Will keep looking.

"Forget pounds and ounces, I'm figuring displacement!"

If we accept that: MBG(+)FGSF(=)HBG(F1)
And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1)
Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT?
PB answer: It depends.