🌍 One Ocean, Five Names The big picture
Earth is really a water planet. About 71% of its surface is ocean, and that ocean holds roughly 97% of all the planet's water. Geographers divide this single connected body of salt water into five named oceans: the Pacific, Atlantic, Indian, Southern and Arctic.
The ocean controls weather and climate, produces about half of the oxygen we breathe, absorbs a large share of the carbon dioxide we release, and soaks up more than 90% of the extra heat from global warming. Yet only about a quarter of the seafloor has been mapped in high detail. Use this site to explore every ocean, the world's major seas and lakes, the canals that join them and the narrow straits that choke world trade.
The five oceans by size
Areas in millions of km². The Southern Ocean is counted separately here, so the older "four ocean" totals are slightly larger for the Pacific, Atlantic and Indian.
🌊 The Five Oceans Size, depth, climate, history
Choose an ocean to see how big and deep it is, what its water temperature and climate are like, the currents that move through it, the history of how people explored it, and what lives and goes wrong there.
Compare the oceans
Figures are rounded and vary a little between sources and by how each ocean's boundaries are drawn.
🗺️ Explore the Map Oceans, seas, lakes, canals and straits
Every place on this page is on the map. Use the buttons to show or hide each kind, tap a pin for a summary, and use the layer button (top right of the map) to switch to the ocean-depth map or to turn on NASA's daily sea-surface temperature picture.
Sea-surface temperature: NASA GHRSST MUR analysis, daily. Warm waters are red and orange, cold waters blue and purple.
🏝️ Major Seas & Gulfs
Seas are parts of the ocean partly enclosed by land, or defined by currents. They are often warmer, saltier or fresher than the open ocean, and many are among the busiest and most contested waters on Earth.
🏞️ Major Lakes
Lakes are inland bodies of water, fresh or salty, and a few are so large they behave like seas, with their own weather, waves, storms and shipping. Some are ancient, some are disappearing within a human lifetime.
The biggest lakes by surface area
Area in thousands of km². The Caspian Sea is a salt lake, and is the largest lake on Earth.
🚢 Great Canals Shortcuts that reshaped the world
A canal is a human-made waterway. The biggest ones join oceans or lakes, save weeks of sailing, and have shaped wars, empires and cities. Some cut straight across land at sea level, others climb hills using locks, which are watertight chambers that raise and lower ships like elevators.
How high do ships climb?
Maximum height ships are lifted above sea level (or between the lakes) in metres. Suez is a sea-level canal with no locks at all.
How long are they?
Lengths in kilometres. The St. Lawrence Seaway figure covers the whole route from the Atlantic to Lake Superior.
⚓ Straits & Choke Points
A strait is a narrow passage of water between two seas or oceans. Because so much trade has to squeeze through a handful of them, they are called choke points: if one is blocked by war, accident or weather, prices and supply chains around the world feel it within days.
🌡️ Climate & Temperature How warm, how cold, and why
Sunlight heats the surface; the deep stays almost uniformly cold. Winds and Earth's rotation then push the warm and cold water around the globe in giant loops called currents, which carry heat from the tropics toward the poles.
Temperature by depth
Typical shapes, not measurements from one place. Near the surface the sun warms the water; in the thermocline it cools quickly; below about 1,000 m nearly all the ocean is 2 to 4°C.
Ocean depth zones
Typical sea-surface temperatures
Typical seasonal range of the sea surface, rounded. Local conditions, depth and weather change the numbers from day to day.
The great currents
Climate patterns that change the whole ocean
📜 History of the Ocean Exploration, crossings and discoveries
People have crossed the ocean for tens of thousands of years, but we only began to measure its depths, map its floor and understand its life in the last 150 years.