Spatterdock, Cow lily
Nuphar advena(Nuphar lutea subspecies advena)
Photos were taken 7-2004 on Lake Norman
Spatterdock is a large plant whose leaves are often floating, however, submerged and emersed leaves are common.
Spatterdock has large heart-shaped leaves, usually with wavy margins. Spatterdock floating leaves are attached to long, stout stems which arise from large, spongy rhizomes. Spatterdock submersed leaves are very thin, attached at the bottom rhizomes. Spatterdock flowers are yellow and “half-opened” at or above the water surface. Flowers are attached to thick round stems that are often six feet long.
http://aquat1.ifas.ufl.edu/nulupic.html