The horned fruits belong to Trapa, while the familiar crunchy water chestnut generally comes from Eleocharis dulcis.
Their appearance, botanical classification, and culinary preparation are completely different.
What About Eating Them Raw?
This is where caution is important.
Traditional preparation generally involves cooking the edible portion rather than casually eating an unidentified raw specimen.
Aquatic plants and their fruits can potentially be exposed to microorganisms from the water in which they grow. Food safety therefore matters.
If you have confirmed that you have an edible species intended for human consumption, follow an established preparation method appropriate for that species.
Do not assume that an unknown wild plant is safe simply because someone calls it a “nut.”
What Should You Do With the Bag in the Photograph?
If your neighbor gave you these and you aren't completely sure what they are, the best move is to identify them before eating them.
Ask your neighbor:
- What are they called?
- Where did they come from?
- Were they purchased or collected?
- Are they intended as food?
- How were they traditionally prepared?
- Do they have a package or label showing the species?
If they came from a market or food supplier, packaging may provide useful information.
If they were collected from the wild, identification becomes much more important.
A local botanist, agricultural extension service, university plant department, or qualified foraging expert may be able to help identify them.
Why You Shouldn't Rely on a Photograph Alone
The fruits in the image have characteristics strongly suggestive of water caltrops, but photographs aren't always sufficient for species-level identification.
Lighting, drying, age, and the angle of the photograph can change their appearance considerably.