At first glance, the strange black fruits in the photograph almost look like something from another planet.
They have dark, hard shells, pointed horns, and irregular shapes that make them difficult to recognize as something edible. If someone handed you a plastic bag full of them without explanation, it would be completely understandable to wonder:
What exactly are these things and how are you supposed to eat them?
The fruits shown in the image appear to be water caltrops, also commonly called water chestnuts, buffalo nuts, bat nuts, or devil's nuts, depending on the species and region. They belong to the genus Trapa and grow in freshwater environments.
Their unusual appearance is one of the reasons they are so fascinating. Despite looking hard and intimidating on the outside, the inside contains a white, starchy kernel that has been eaten in parts of Asia and other regions for generations.
But there is an important point to understand before trying them:
You shouldn't simply wash one and bite into it raw.
Proper identification, cleaning, and cooking are important, particularly because freshwater plants and fruits can potentially carry microorganisms or parasites when consumed raw.
What Are Those Strange Horned Fruits?
The fruits in the photograph have a distinctive appearance.
They are dark brown to almost black on the outside, with a hard shell and curved projections resembling horns.
This unusual shape is characteristic of water caltrops.
Water caltrops are aquatic plants that grow in ponds, lakes, slow-moving waterways, and other freshwater environments. Their fruits develop underwater and eventually become hard, woody structures.
Depending on the species, the fruit may have two, three, or four prominent projections.
That's why people around the world have given them memorable names.
Some varieties are known as:
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Water caltrop
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Horned water chestnut
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Buffalo nut
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Bat nut
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Devil's nut
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Singhara
The exact common name varies considerably from one country or region to another.
Why Do They Look Like Little Horned Animals?
The strange shape isn't accidental.
Those hard projections are part of the plant's reproductive strategy.
When the fruit matures, its shape and weight help it interact with the surrounding environment and eventually contribute to the plant's reproduction.
The hard exterior also protects the edible seed inside.
From a human perspective, however, the horns create one immediate problem:
They're not exactly easy to peel.
Unlike an apple or peach, you can't simply bite through the skin.
The shell is hard and woody, so the fruit needs to be opened carefully.
What Is Inside?
This is where the surprise comes in.
Inside the dark shell is a relatively pale, firm, starchy edible portion.
When properly cooked, the flesh can have a texture somewhat reminiscent of a chestnut.
It can be mildly sweet, nutty, earthy, or starchy depending on the species and preparation.
That's why these fruits have traditionally been used in various dishes.
The contrast is striking:
Outside: dark, hard, and covered in horns.
Inside: pale, starchy, and edible.
It is one of those foods that looks completely different before and after preparation.
Are They Actually Related to Chestnuts?
Despite the name "water chestnut," water caltrops are not the same thing as the familiar Chinese water chestnut (Eleocharis dulcis).
This is an important distinction.
Chinese water chestnuts are aquatic sedge plants that produce small, rounded underground corms.
Water caltrops are fruits produced by plants in the genus Trapa.
The two foods can both be eaten and have somewhat starchy textures, but botanically they are quite different.
So if someone calls these "water chestnuts," the name can be confusing.
How Do People Eat Them?
Traditionally, the edible interior is obtained by cooking the fruit and then removing the hard shell.
Preparation varies depending on the region and species.
One common approach is to:
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Wash the fruits thoroughly.
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Cook them by boiling or steaming.
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Allow them to cool enough to handle safely.
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Crack or cut away the hard outer shell.
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Remove the edible kernel.
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Eat the cooked kernel on its own or incorporate it into another dish.
The exact cooking time can vary according to size and species, so it's best to use a reliable recipe specific to the type you have.
Why Cooking Matters
This is probably the most important part of the story.
Because water caltrops grow in freshwater environments, eating them raw isn't a good idea.
Freshwater plants and aquatic produce can become contaminated with microorganisms or parasites from the environment.
One parasite of particular concern in some regions is Fasciolopsis buski, a foodborne intestinal fluke associated with raw or inadequately cooked aquatic plants.
This doesn't mean every water caltrop is contaminated.
It means that raw freshwater plant foods can carry risks that cooking helps reduce.
For that reason, traditionally prepared water caltrops are generally cooked thoroughly before consumption.
Don't Treat Them Like a Normal Fresh Fruit
If you receive a bag of these from a neighbor, don't assume they're ready to eat simply because they look clean.
The safest approach is to first establish:
What species are they?
Where did they come from?
Were they harvested from a clean water source?
Have they been stored properly?
Are they intended for human consumption?
This matters because a photograph can suggest an identification, but it cannot guarantee the species or determine whether a particular batch is safe to eat.
If you're uncertain about their identity or origin, it's better not to experiment with eating them.
What Do Cooked Water Caltrops Taste Like?
People often describe the edible interior as relatively mild.
The texture is usually more important than the flavor.
Depending on the species and preparation, it may be:
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Firm
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Starchy
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Slightly crunchy
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Nutty
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Mildly sweet
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Similar in texture to a chestnut
That's one reason they're often used in dishes where the texture can stand out.
They don't necessarily have an overpowering flavor.
Instead, they can absorb or complement the flavors of the foods they're cooked with.
How Are They Used in Cooking?
In regions where water caltrops are traditionally eaten, they can be prepared in several ways.
The cooked kernels may be:
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Eaten as a snack
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Added to savory dishes
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Mixed into rice dishes
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Included in soups
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Used in stir-fries
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Ground into flour
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Added to traditional sweets
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Used in porridge or other grain-based foods
Some cuisines also dry and grind the edible portion into flour.
That flour can then become an ingredient in different traditional preparations.
A Traditional Food in South Asia
Water caltrops have a particularly long culinary history in parts of South Asia.
In India, for example, a type of water caltrop commonly known as singhara has been eaten for generations.
The fruit is often boiled before the shell is removed.
The edible portion can then be eaten directly or processed into flour.
Singhara flour is also used in some traditional foods, including dishes prepared during certain religious fasting periods.
The food's popularity is partly due to its starchy nature and versatility.
Water Caltrops in Asian Cuisine
Different species and varieties of Trapa have also been used in East and Southeast Asian food traditions.
Preparation methods differ considerably from one region to another.
Some communities roast or boil the fruits.
Others process the edible portion into flour or incorporate it into traditional recipes.
This is a good reminder that foods that look unusual to one person may be completely familiar to another.
A bag of horned fruits might seem mysterious in one household while being a seasonal favorite somewhere else.
Are Water Caltrops Nutritious?
The edible portion contains carbohydrates and can provide several nutrients, although the nutritional composition varies according to species and preparation.
Because the kernel is starchy, it can provide energy.
Depending on the specific variety, it may also contribute:
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Fiber
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Potassium
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Minerals
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Small amounts of protein
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Other plant nutrients
However, it's important not to exaggerate the health benefits.
You may find online claims describing water caltrops as a cure for various illnesses or as a powerful "detox" food.
Those claims often go well beyond what scientific evidence supports.
It's better to think of them simply as a traditional starchy food that can be part of a varied diet when properly identified and prepared.
Can You Eat Them Raw?
This is where you should be cautious.
Even if some people have eaten aquatic plant foods raw, that doesn't mean doing so is safe.
Freshwater environments can contain parasites and microorganisms that may be transferred to edible plant material.
The risk depends on the species, environment, harvesting conditions, and local prevalence of pathogens.
Therefore:
Don't assume raw is safe just because someone online says they ate one raw.
Proper cooking is a much safer approach.
What About the Hard Shell?
The exterior isn't the part you eat.
Its main job is protection.
The shell can be quite hard, and the horn-like projections can also be sharp enough to cause discomfort or minor injury.
That's why opening them requires care.
A sturdy kitchen tool may be necessary, and you should avoid trying to crack them aggressively in your hand.
If you've never prepared them before, following a region-specific recipe or preparation guide is preferable to improvising.