One discerning characteristic of submerged plants is their flaccid or soft stems, which is why they do not usually rise above the water 's surface. Emergent Plants are rooted plants often along the s.line that stand above the surface of the water cat.s . The stems of emergent plants are somewhat stiff or firm..Emergent Plants Water-willow American Water-willow White Water Lily Fragrant Water Lily Yellow Water Lily Mexican Water Lily . Search: About/Credits .Identify pond and lake weed types and learn how to control acquatic weeds, It grows in expansive mats that block sunlight to submerged aquatic plants, .Duckweed can overtake a pond and completely cover the surface robbing the pond of light and oxygen. Duckweed. Duckweed is a small free floating plant about 1/8 to 1/4 in diameter. Watermeal. Floating Leaf Pond Weed. Water Lilies. Spatterdock. Filamentous Algae..