Anemones are fascinating creatures found in the ocean. With their delicate-looking tentacles and brilliant colours, they can look almost like underwater flowers swaying gently in the current. But despite their flower-like appearance, anemones are animals—and their changing colours and movements are part of what makes them so interesting.

A Rainbow Beneath the Waves

Anemones come in an incredible variety of colours. Depending on the species and their environment, you may see them in shades of red, orange, pink, purple, blue, green, yellow, brown and white. Some have a single colour, while others have contrasting tips, stripes, or glowing-looking patterns.

But why are they so colourful?

Their colours can come from natural pigments within their tissues, as well as from microscopic organisms called zooxanthellae that live inside many anemones. These tiny photosynthetic partners use sunlight to produce energy, and in return, the anemone provides them with a safe place to live.

The amount and type of these microscopic organisms, along with the anemone’s own pigments, can influence how it looks.

This is also why two anemones of the same species may not always look exactly alike. Light levels, water conditions, nutrition, genetics and the presence of different symbiotic organisms can all contribute to differences in colour.

Why Do Anemones Open?

When an anemone is open, its tentacles spread out into the water. This is often when it looks most like a colourful underwater flower.

One important reason anemones open is feeding. Their tentacles contain specialised cells called nematocysts, which can sting and help them capture tiny prey drifting through the water. When the tentacles are extended, the anemone has a larger area with which to interact with the surrounding water.

Anemones may also open when conditions are comfortable and they are able to make use of sunlight. Species that have photosynthetic partners can benefit from exposing their tissues to light.

In a healthy reef environment, an anemone may therefore spend long periods fully expanded, gently moving its tentacles with the current.

A Poisonous Home—and a Safe Haven

One of the most remarkable things about anemones is that their stinging tentacles can be dangerous to many small marine animals. The specialised cells in their tentacles can release tiny harpoon-like structures containing venom, helping the anemone capture prey and defend itself.

Yet there is one little fish that has found a remarkable way to live among these dangerous tentacles: the clownfish.

Clownfish and certain species of sea anemones have a mutually beneficial relationship known as symbiosis. The clownfish can live among the anemone’s stinging tentacles, gaining protection from predators that are unable or unwilling to venture into the anemone.

The relationship benefits the anemone too. The clownfish may bring food to its host, provide nutrients through its waste, and help keep the anemone clean by moving around it and removing debris. Its constant movement may even improve water circulation around the anemone.

So while an anemone’s tentacles can be a dangerous place for many creatures, for a clownfish they can become a safe and protected home.

It is a wonderful example of how different species can evolve together and depend on one another. What looks like a dangerous creature to one animal can become a sanctuary for another.

And Why Do They Close?

Seeing an anemone suddenly shrink or close can look alarming, but closing is often completely normal.

Anemones can contract their bodies and pull in their tentacles when they need to protect themselves. They may do this when they are disturbed, touched, exposed to strong water movement, or experiencing changes in their surroundings.

They may also close while digesting food or expelling waste. Sometimes an anemone simply needs to retract for a while before opening again.

Changes in light can also affect their behaviour. Some anemones expand more during daylight, while others may change their appearance depending on the time of day and their individual rhythms.

Anemones Are More Active Than They Look

Although anemones may appear to be simple, stationary creatures, they are surprisingly responsive to their environment. Their tentacles constantly move with the water, and their bodies can expand, contract and change shape.

Some species can even move from one location to another. They may slowly crawl across a surface or use their pedal disc—the muscular structure at their base—to relocate when conditions are not suitable.

This ability to respond to light, water movement, food and their surroundings is part of what makes watching anemones so captivating.

Every Anemone Has Its Own Personality

Anemones are living creatures that naturally change throughout the day. Their colours, shapes and movements are all part of the story of life beneath the waves.

A Living Underwater Flower

Anemones may look like flowers, but their behaviour reminds us that they are fascinating marine animals with their own ways of feeding, protecting themselves and responding to their environment.

Their spectacular range of colours makes them beautiful to look at, while their habit of opening and closing gives us a glimpse into the hidden rhythms of life underwater.

And perhaps their most beautiful story is the unlikely friendship between the anemone and the clownfish: a creature armed with venomous tentacles providing a safe home for a tiny fish, while the fish, in return, helps its host thrive.

So the next time you see an anemone, take a moment to watch it. Whether it is proudly displaying its colourful tentacles, sheltering a tiny clownfish, or quietly tucked away, it is doing exactly what it has evolved to do—respond to the ever-changing world around it.