Pickerelweed or Pickerel Rush
Pickerelweed is a very common immersed plant. It is a prolific grower and can cover large areas.
Pickerelweed typically grows to about two to three feet tall. Its leaves are large, up to five inches wide, and are usually twice as long. Leaf shapes are variable but are usually lance-shaped. The easiest way to recognize pickerelweed is by its spike of violet-blue flowers.