Common Yellow Waterlily or Banana Waterlily (Nymphaea mexicana) is a hardy water lily. It stays relatively small 2-4 feet wide. It is considered hardy to at least USDA Zone 6 (-10º F/-23º C), perhaps more depending on locality and shelter.
White Floating Hearts (Nymphoides aquatica) is not a waterlily but the leaves somewhat resemble one. The flowers are quite different. It is in an unrelated family: the Bog-bean Family (Menyanthaceae). It is considered hardy to at least USDA Zone 8 (10º F/-12º C).
Both plants are native to parts of the southeastern United States, as well as Mexico.