Water caltrop in American English

I have never seen them, but this blogger reports finding them in Berkley, CA, under the name caltrop nuts. Based on the name of the blog, I infer that they are still considered "exotic" in America. http://soulcocina.blogspot.com/2006/07/exotic-ingredients-strange-fruit.html?m=1

I often find them on the banks of the Hudson river in NY. I've collected them for years (thinking they looked quite extraterrestrial) and showed them to people, asking for identification. "Devil Pod" was the only answer I ever got.

Wikipedia lists them as water caltrops first, with the other names following behind. If you're looking to market them, that's a nice, distinctive name that won't be confused with anything else.