At first glance, these strange black objects hardly look like food. Their hard shells and curved horns make them resemble tiny bats or miniature bull heads, so it’s understandable to wonder why anyone would hand over an entire bag and expect you to eat them.

They are water caltrops, the horned fruits of aquatic plants in the genus Trapa. They are also known by names such as bat nuts, buffalo nuts, or horned water chestnuts, although they aren’t the same plant as the round Chinese water chestnuts commonly found in stir-fries.

The part you eat is hidden inside that intimidating shell. Once opened, a water caltrop contains a pale, starchy kernel. Traditionally, the fruits are boiled or roasted, and the cooked interior can be eaten on its own or incorporated into other dishes.

The simplest preparation is to wash them thoroughly and boil them before eating. One common method is simmering them for roughly 30–40 minutes, allowing them to cool, then carefully cracking or cutting open the hard shell and removing the white flesh inside. Because preparation guidance warns about risks associated with eating them raw, thoroughly cooking unfamiliar water caltrops is the safer choice.

So your neighbor didn’t give you a bag of bizarre animal claws—they gave you an old-fashioned edible aquatic crop. Once cooked and peeled, the unusual black shell reveals the part people actually eat, with a mild, starchy character often compared with chestnuts. Just be careful handling those pointed horns while opening them.