Any help is greatly appreciated. Leaves are typically in whorls of 4. Growing in about 30-60 cm of water. (Sorry, not the greatest pictures.)
Several seen in shallow water around island near boat landing
Spent 30 minutes collecting along shore (1-4 feet deep) sweeping net quickly across marsh bottom and through vegetation. Used D-net with 1/4 inch mesh approx. 14 inches wide and 10 inches tall with 5 foot long handle. Collected no fishes. 95% of catch was what appeared to be one species of Lymnaeidae snail and a few aquatic insects (2 Zygoptera, 1 Anisoptera, 1 Dytiscoidea).