Submerged aquatic vegetation consists of a taxonomically diverse group of plants that lives entirely beneath the water surface. This diverse group of aquatic plants includes species of angiosperm vascular plants, mosses, and liverworts, and macroalgae (seaweeds). Their underwater growth habit separates them from other kinds of aquatic plants that are free-floating, have floating leaves, or are emergent above the water surface.

Almost all species of submerged aquatic plants live in freshwater ponds, lakes, rivers, streams, and wetlands, and shallow marine waters. They can occur in ponds with an acidic pH less than 4 or in alkaline waterbodies with pH greater than 10, but they tend to be most rich in species at pHs of 6 to 8. Only a few angiosperm species occur in brackish estuarine or marine habitats, including the eelgrass (Zostera marina), widgeon grass (Ruppia maritima), and turtle-grasses (Thalassia species). No aquatic mosses or bryophytes occur...