“Why should we spend money exploring the ocean?” is a fair question, and it deserves a better answer than “because it’s there”. The good news is that ocean exploration has a long record of practical returns, many of which people use every day without knowing where they came from. Below are eight of the clearest, each with real examples. I have tried to avoid vague claims and stick to benefits that are well documented.

I come to this as a diver and reef keeper rather than a professional scientist. But I have spent enough time underwater, from Bonaire and Cozumel to Fiji and the Red Sea, and enough years running coral systems at home, to know how much we still don’t understand, and how much depends on finding out.

1. Understanding climate and weather

The ocean is the engine of Earth’s climate, and we cannot predict climate or weather without exploring it.

The ocean stores far more heat than the atmosphere and moves it around the planet through currents such as the Gulf Stream. International assessments estimate that it has absorbed around 90 percent of the extra heat trapped by greenhouse gases in recent decades, and roughly a quarter of the carbon dioxide humans have emitted. Measuring that requires instruments throughout the ocean, including the international fleet of Argo floats that profile the upper ocean every few days. Ocean data also feeds daily weather forecasts and seasonal outlooks: El Niño, a periodic warming of the tropical Pacific, affects rainfall, droughts and storms around the world, and forecasting it depends on monitoring the ocean. Our page on physical oceanographers explains how this work is done.

2. Warning us about hazards

Ocean exploration saves lives by helping predict tsunamis, storm surges and coastal hazards.

After the 2004 Indian Ocean tsunami killed more than 200,000 people, tsunami warning networks were expanded around the world. They rely on seafloor pressure sensors, such as NOAA’s DART buoys, which detect the passage of a tsunami in the deep ocean and relay data by satellite. Mapping undersea faults and unstable slopes helps identify where tsunamis and submarine landslides are likely. Hurricane forecasts depend on knowing how much heat lies in the upper ocean, because warm water fuels rapid intensification. Coastal mapping supports planning for storm surges and sea-level rise. Each of these depends on having explored and measured the ocean first. When a warning reaches a coastal town in time, it is the product of decades of seafloor mapping, instrument development and data sharing that most people never see.

3. New medicines and biotechnology

Marine organisms produce chemical compounds unlike anything on land, and several have become medicines.

The cancer drug cytarabine, used against leukaemia, was developed from compounds first isolated from a Caribbean sea sponge in the 1950s. Ziconotide, a powerful painkiller, is a synthetic version of a toxin from a cone snail. Trabectedin, used for certain soft-tissue cancers, comes from a Caribbean sea squirt. Beyond drugs, the green fluorescent protein from the jellyfish Aequorea victoria became one of the most important tools in biology, earning its discoverers the 2008 Nobel Prize in Chemistry, and heat-tolerant enzymes from microbes living around hydrothermal vents are used in laboratory DNA work. Sponges are among the richest sources of these compounds, which is one reason I find them fascinating; see sea sponge facts.

4. Feeding the world

Seafood is a major source of protein for billions of people, and sustainable fishing depends on knowing the ocean.

Fisheries scientists use surveys, acoustic mapping, tagging and ocean data to estimate how many fish there are, where they spawn and how they respond to changing temperatures. Exploring spawning grounds, nursery habitats such as mangroves and seagrass, and deep-sea ecosystems helps managers set catch limits and protect the places fish depend on. Upwelling zones, where currents bring nutrient-rich water to the surface, support some of the largest fisheries on Earth, and understanding them requires ocean exploration. As fish populations shift with warming water, that knowledge becomes even more important.

5. Discovering new life and ecosystems

Almost every deep-sea expedition finds animals no one has seen before.

The most famous discovery came in 1977, when scientists in the submersible Alvin found communities of giant tube worms, clams and crabs living around hydrothermal vents on the Galápagos Rift, powered by bacteria that use chemical energy instead of sunlight. That changed ideas about where life can exist, on Earth and elsewhere. The decade-long Census of Marine Life, completed in 2010, added well over a thousand newly described species and identified thousands more awaiting description. Estimates suggest most marine species remain undiscovered; see how many ocean species are undiscovered. Each discovery adds to our understanding of evolution, ecology and the potential uses of marine life.

6. Maps, navigation and the internet

The modern economy runs across and beneath the ocean, and it depends on accurate maps of the seafloor.

Most international internet and telephone traffic travels through undersea fibre-optic cables, not satellites. Laying them safely requires detailed surveys to avoid steep slopes, active faults and areas prone to landslides. Shipping, which carries the large majority of world trade by volume, depends on accurate nautical charts. Offshore wind farms, pipelines and ports all need seafloor information. Yet only about a quarter of the global seafloor has been mapped in high resolution; see why we have better maps of Mars than of the ocean. Ocean exploration fills those gaps, one survey line at a time.

7. Recovering history beneath the waves

The seafloor is the world’s largest museum.

Shipwrecks preserve objects, cargo and sometimes whole ships from every era of seafaring. The Antikythera mechanism, an ancient Greek astronomical calculator recovered by sponge divers from a wreck in 1900–1901, transformed our understanding of ancient technology. Deep-water exploration has located the Titanic, wartime fleets and long-lost explorers’ ships, and drowned landscapes on continental shelves preserve evidence of people who lived there when sea levels were lower. Wrecks are also among the most memorable dives I’ve done; the wreck-diving guides on this site, from Grenada to Vanuatu, show how history and marine life merge on the seafloor. See our shipwrecks section for more.

8. Protecting coral reefs and marine life

We cannot protect what we have not found, mapped and understood.

Exploration has revealed deep-water coral reefs in cold, dark water off Norway, Ireland and the southeastern United States, as well as mesophotic reefs in the twilight zone below normal diving depths that may serve as refuges for shallow reefs. Mapping and surveying have guided the creation of marine protected areas, including huge reserves in the Pacific. Monitoring reefs before, during and after marine heatwaves tells us which corals survive bleaching, which matters for restoration. As someone who has spent years growing corals from fragments, I know how much knowledge goes into keeping corals alive in a controlled system. On a real reef, that knowledge comes from exploration and long-term monitoring.

Exploring responsibly

Exploration has costs too, and the case for it is strongest when it is done carefully.

Deep-sea ecosystems are often slow-growing and fragile. Deep-water corals and glass sponges can be centuries or even thousands of years old, and a single trawl or careless sampling run can destroy what took that long to grow. Some of the most heated debates in ocean science today concern deep-sea mining, where exploration for metals on the seafloor could open the door to large-scale disturbance of habitats we barely understand. Good ocean exploration therefore tends to favour cameras, sonar, environmental DNA and minimal sampling over collecting large numbers of specimens. It also shares data openly, so that one expedition’s findings can inform many others. The same principle applies on a small scale for divers: look, photograph, don’t touch, and leave the reef as you found it. Exploration that ends up damaging the places it reveals defeats its own purpose.

For a comparison of how ocean and space exploration are funded, see ocean exploration vs space exploration, and for the people who do this work, what oceanographers do and how ocean exploration has changed our understanding of aquatic ecosystems.