Nuphar lutea
yellow pond-lily, spatterdock

Nuphar lutea
Nuphar lutea
Wiki Commons, GNU
USDA Plant Database
Botanical name: Nuphar lutea
Common name: yellow pond-lily, spatterdock
Group: dicot
Family: Nymphaeaceae
Growth type: forb/herb
Duration: perennial
Origin: native
Plant height: just above the water surface
Foliage: dark green, 4-8", rounded to ovate to lance shaped, narrow V-notch
Flower: yellow, 1 to 2-1/2" across
Flowering time: late May to mid September
Habitat: ponds, slow streams
Range in New Jersey: statewide
Heritage ranking, if any: n/a
Misc. Various species (N. advena, N. variegatum, N. microphyllum) have been "lumped" into N. lutea. Taxonomy of Nuphar in North America is not very clear; in fact, genetic studies indicate that they may not be related to the Eurasian Nuphar and may in fact warrant additional names.
"lutea", yellow. 
Insect pollinated.
The roots and seeds are edible and were used by some Native American tribes by roasting and grinding into flour, and for thickening soups.