It's not called the blue planet for nothing. The ocean covers up to 71% of the Earth's surface and 90% of the biosphere. It is integral to life and provides anywhere between 50 to 80% of the planet's oxygen, making it a vital part of the carbon cycle. The ocean's origins are still unknown, but it is thought to have formed 4.4 billion years ago, providing a catalyst for early life-forms.

Despite its sheer size, we actually know very little about the ocean. In fact, over 80% of this underwater realm has yet to be mapped or explored. Scientists are working to unlock its mysteries, which could help us better understand environmental change and how to manage vital ocean resources in times of climate change.

We do know that the ocean plays a major role in regulating the Earth's climate by absorbing solar radiation, distributing heat and driving weather patterns. But climate change is already starting to disrupt this balance, affecting the ocean's ability to perform key ecosystem tasks, such as carbon storage and oxygen generation.

The ocean is home to at least 230,000 known species. Coral reefs on the sea floor provide a safe-haven for invertebrates like crabs, starfish and mollusks, as well as colorful reef fish. Plant life flourishes in the shallow depths, while bigger creatures like sharks, whales and dolphins roam the deep open waters.

Unsurprisingly, scientists also think up to two-thirds of all ocean species may still be undiscovered. But researchers are finding new species every year — many of them unlike anything found before, such as this squidworm (pictured), discovered in the Celebes Sea in 2007. What else might be lurking down there is anyone's guess.

But the ocean is under pressure. One of the most obvious examples being the increase of coral bleaching events in reefs around the world. Increased temperatures and pollution stress corals, causing them to expel a special kind of algae which allows them to grow and reproduce, leaving behind a ghostly skeleton. Some corals can recover, but prolonged stressors increase the chances of reef mortality.

Climate change is also seriously impacting marine species, with recent research showing that local populations of fish, mollusks and crabs are disappearing at twice the rate of land species. Extreme temperatures are the main culprit, as the ocean offers fewer places to hide from the heat. Sadly, the majority of ocean species won't be able to evolve fast enough to adapt to the changing conditions.

In the cryosphere — parts of the Earth's surface covered in solid water, including ice and snow — atmospheric warming is causing the melting of glaciers and ice. The current melting event is already contributing to global sea level rise and could also lead to higher levels of ocean acidification, thanks to methane released from seafloor permafrost in the Arctic Ocean.

Humans are inextricably linked to the ocean. For thousands of years communities have thrived along the coast, relying on it for food and livelihoods. Today, more than one billion people live in low-lying coastal regions which are likely to be impacted by rising sea levels.

But this connection has come at a cost. Just 13% of the world's oceans are completely free from human activities such as fishing, with almost no true wilderness left along coastal areas. Technological advancements mean even the farthest reaches of ocean in the Arctic are no longer untouched. Protecting the remaining wilderness will be a challenge for generations to come.

Plastic, an amazingly versatile material, is indispensable in construction and packaging. But it's also a global scourge. In this photo, tons of waste, including plastic bottles, used tires and various non-organic materials, can be seen clogging the Drina River, forming a floating landfill near Visegrad, Bosnia and Herzegovina.

On this beach in the Philippines, children jump barefoot over plastic waste — left behind by typhoons. The garbage, once carelessly discarded, has traveled through rivers before ending up in the sea and finally washing up on the beach. But it's not just water swallowing this debris. Animals are also at risk.

Nina Gomes fishes a discarded plastic bag out of the sea near the famous Copacabana beach in Rio de Janeiro, Brazil. Every year, the country produces an estimated 11.3 million tons of plastic waste, of which only around 1.2% is recycled. Much of that plastic waste ends up in the oceans, endangering the marine environment.

In the South African township of Alexandra, a net forms a plastic barrier in the Jukskei River. These volunteers are working to carefully remove the accumulated waste from the net. But such measures alleviate the symptoms, not the causes. Waste remains a challenge — not only here, but worldwide.

Plastic waste covers the sand at Badhwar Park beach on the Arabian Sea coast in Mumbai, India. With a population of over 1.4 billion, India is one of the largest consumers of plastic in the world. According to estimates, the country produces around 3.5 million tons of plastic waste every year, of which only a small proportion is recycled.

In a shanty town in the Indian capital, New Delhi, where every inch of the landscape is littered with plastic waste, bags of garbage wait to be sorted by collectors hoping to sell them on.

On Earth Day 2024, these environmental activists in Seoul held up posters calling on the world to "stop plastic pollution!" Talks to negotiate a global treaty to curb plastic waste failed to reach a deal in South Korea in early December, with some oil-producing countries rejecting restrictions and targets for decreasing plastic production. The negotiations are due to resume next year.

In Indonesia, mountains of plastic waste pile up on the roadsides and obstruct traffic. With a population of over 11 million people in its capital alone, Indonesia produces around 6.8 million tons of plastic waste every year, a significant proportion of which is not disposed of properly. Around 620,000 tons of this ends up in the ocean.

A priest sits among the garbage left behind by worshippers during the Kuse Aunsi festival at the Gokarneshwor temple in Kathmandu, Nepal. One thing is clear: the plastic crisis requires bold political decisions and a global rethink. Without action, plastic will continue to pollute rivers and oceans, threatening life and preventing a sustainable future.

Camels in underwater photography? The winning photo in the portrait category of the "Underwater Photographer of the Year" competition was not taken in a vast ocean, but in the drinking bucket of a herd of camels. The camel's hairy snout gently pushes through the surface of the water toward the camera, a kiss seems inevitable.

The main winner of the competition is this photo by Alvaro Herrero entitled "Radiant Bond." The Spanish photographer, whose artist name is Mekan, captured this majestic moment of two humpback whales in French Polynesia. The whale accompanies her young to the surface for a few breaths, surrounded by the bright rays of the morning sun.

This photo from an underwater cave in Yucatan, Mexico, transports the viewer into a dreamlike world. Surreal stone formations grow from the ceiling and floor in the clear water. Sophisticated diving techniques and photographic accuracy contributed to the magic of this image.

The expectations of an underwater photo are turned upside down in this shot: Is the diver flying through the northern lights or are we seeing special effects from an old science-fiction movie? No, it's a diver swimming through the underground lakes of a cave in Cancun, Mexico. The photographer patiently chose the right time of year and weather conditions to create the fantastical lighting effects.

This shipwreck lies more than 100 meters (about 320 feet) below the surface, off the coast of Egypt. Immersed in dim light, overgrown with seaweed, algae and coral, surrounded by shoals of fish: this award-winning photo awakens a thirst for adventure.

Who comes to visit me in my green-blue underwater kingdom, this seal seems to ask in a friendly manner. The portrait of the seal was taken off the rugged British Atlantic coast near North Devon. A group of gray seals lives off the island of Lundy, in a marine area that has been protected since 1973.

These Indonesian fishermen are carrying a captured tiger shark out of the water. One of the millions of sharks killed every year, this one has been caught in the men's net. The viewer suddenly becomes aware of the cruel reality of this toll through the photo. The haunting image was chosen as the winner of the "Save Our Seas" category.

The blue marlin is a lightning-fast, feared hunter in the underwater world. Here, the large swordfish plunges into a school of sardines at high speed as the smaller fish scatter in the bright blue water. Eduardo Acevedo captured this moment full of movement in the midst of the hunt, a photographic feat that was recognized by the 2025 jury.