This is an intriguing pond plant that I acquired last spring. It bloomed a couple of weeks ago. I have this "meadow beauty", Rhexia virginica in a regular flower pot on the patio--not in a pond--but I keep the potting media wet all the time. R. virginica is in Family Melastomataceae, a plant group more typical of tropical areas, but this one occurs in North America as far north as Wisconsin. Here's a better look at the blooms. R. virginica has quite prominent anthers. I remember seeing a number of different Melastomataceae out in the woods in Costa Rica and R. virginica is similar in overall appearance to those plants, having almond-shaped leaves with prominent parallel veination and showy, four-petaled blooms. Many of the tropical ones grow as epiphytes, but R. virginica is a wetland plant especially characterisitc of wet, sandy, acid soils.