Mary Sue asked about, among others, Ipomoea aquatica and Nymphoides aquaticum (note that in the older literature the genus was sometimes treated as neuter, thus Nymphoides aquaticum - something to keep in mind if you're doing a Google search). Ipomoea aquatica is a widely grown vegetable, now marketed here in the US primarily in Asian markets. It's sometimes called "water spinach". Nymphoides aquatica is a common pond plant in the eastern US and maybe elsewhere. It's the "banana plant" of the aquarium trade. These are gentian family plants with flowers a bit like those of Menyanthes. Jim McKenney Montgomery County, Maryland, USA, USDA zone 7, where it may reach 65 degrees F today.