There are 49 landlocked countries in the world, and then there’s Kyrgyzstan. The Central Asian country is located the farthest from any ocean — it’s 1,620 miles from the nearest coastline on the Indian Ocean. Although Kyrgyzstan is the farthest country from the sea, it isn’t home to the exact point on the globe farthest away from any coastline. That honor belongs to the Dzungarian Basin in northwest China.

Blue whales are found in waters all over the world, but they don't venture north to the Arctic Ocean, which is too cold for them to live. The Southern Ocean, though also cold, isn't at such a polar extreme due to the landmass of Antarctica at the globe's most southerly point. The whales, which are the largest animals on Earth, can grow to be 110 feet long and 330,000 pounds.

About 75 miles north of Puerto Rico lies the Puerto Rico Trench, a chasm in the Atlantic Ocean that is about 1,090 miles long and 60 miles wide. At its deepest point, the Milwaukee Depth, the Puerto Rico Trench is 27,493 feet below water, making it the deepest point in the Atlantic Ocean. Only one person, explorer Victor Vescovo, has been to the floor of the Milwaukee Depth.

From the ancient Greek words meaning "depth" and "measure" comes the English word for the study of ocean depth: bathymetry. Bathymetry illustrates the land that lies underwater, similar to the way topographic maps represent the three-dimensional features of overland terrain. Bathymetric models are how we know where the deepest parts of our oceans can be found.

The Sargasso Sea is the world's only sea without a land border. The vast patch of ocean is instead defined only by ocean currents, and lies within the Northern Atlantic Subtropical Gyre. Currents including the Gulf Stream establish the sea's boundaries, and also keep its unique sargassum seaweed from spreading to the rest of the world's oceans.

Yes, waterfalls do exist under the ocean’s surface. The Denmark Strait is not only home to the largest underwater waterfall, but also the largest waterfall found anywhere on the planet. The strait separates Iceland from Greenland, and it’s where warm water from the Irminger Sea meets the glacial water from the Nordic Seas. As a result, the warm water rises, while the denser cold water sinks, creating a powerful downward flow.

The Gulf Stream is an extremely long and powerful ocean current that brings warm water from the Gulf of Mexico across the Atlantic Ocean to northern Europe. The Gulf Stream is caused by circular currents and powerful winds called oceanic gyres, which keep the waters of the world's oceans constantly in motion. The stream has existed for millions of years, but humans first discovered it in the early 1500s.

About 300 million years ago, Earth had one massive supercontinent called Pangea. Surrounding that was a giant superocean containing nearly all of the world's water, which was called Panthalassa. Since that time, the continents have shifted to their own separate places, and Panthalassa has been divided into the five oceans of today.

The depth of the ocean is categorized into five layers. The first is the Epipelagic Zone, or the Sunlight Zone, which extends about 600 feet below the water's surface, followed by the Mesopelagic or Twilight Zone. Then comes the Bathypelagic or Midnight Zone, and below that is the Abyssopelagic Zone, where most of the ocean floor is. Finally comes the Hadal Zone in ocean trenches — the deepest parts under the water.

Scientists estimate that 50% to 80% of the world’s oxygen comes from our oceans, thanks to its extensive collection of small, usually microscopic, organisms called phytoplankton. One type of phytoplankton, Prochlorococcus, is a tiny plant-like bacteria that alone is responsible for creating 20% of the ocean’s oxygen — more oxygen produced than all tropical rainforests combined.

Extending more than 40,000 miles around the Earth, the underwater Mid-Ocean Ridge is the planet's longest mountain chain. Rising along divergent plate boundaries between nearly every continent, the ridge can be subdivided into smaller ranges like the Mid-Atlantic Ridge and the East Pacific Rise, both of which have peaks that are found an average of 8,200 feet below the water's surface.

The world's oceans are subdivided into various marginal seas, and the Indian Ocean is no exception. It includes the Arabian Sea, which borders Iran and Pakistan to the north; the Andaman Sea, which borders Myanmar and Thailand; and the Red Sea, which lies between Africa and Asia. It also has the Timor Sea, the Persian Gulf, the Mozambique Channel, the Laccadive Sea, the Bay of Bengal, and more.

A lot less ominous than the Bermuda Triangle, the Coral Triangle is located in the western Pacific Ocean and includes the waters of Indonesia, Malaysia, the Philippines, Timor Leste, Papua New Guinea, and the Solomon Islands. The region is named for the huge numbers of coral that call it home, including nearly 600 species of reef-building corals, or 75% of the world’s coral species.

Ocean tides are created by the moon's gravity. As Earth rotates each day, the location of the moon relative to Earth also changes, which causes different parts of the ocean to rise or fall. Water that is closest to the moon gets pulled up ever so slightly, creating high tide. The sun's gravity also has an effect on the tides, though it is much less powerful.

With average salinity approaching 37 grams per liter of water, the Atlantic Ocean is the saltiest of the world's oceans. While the reasons are not entirely understood, the ocean's saltiest regions occur where evaporation is highest. Also, trade winds carry the fresh water evaporated from the Atlantic across the Isthmus of Central America, adding fresh water to the Pacific and leaving the Atlantic with the salt.

The Strait of Magellan is a channel of water at the tip of South America connecting the Atlantic and Pacific Oceans. The Strait is about 350 miles long and lies mostly in Chilean territory. The strait is named for Portuguese explorer Ferdinand Magellan, who in 1520 became the first European explorer to sail through the channel. Although it is less strategic for world trade since the opening of the Panama Canal in 1914, it remains in frequent use by Argentina and Chile.

About 124 miles east of the Mariana Islands lies the Mariana Trench, which is not only the deepest point in the Pacific, but also the entire world. At the trench's deepest point, named Challenger Deep, the distance to the surface is nearly seven miles. If Mount Everest were dropped into the trench, it would be completely submerged with more than a mile to spare.

Most of the waves on the surface of the ocean are simply caused by wind. As wind blows across the water, the continual disturbance creates a wave crest, which can then travel along until it breaks on a coast or in the middle of nowhere. Waves can be caused by tides, currents, earthquakes, or even divers doing a cannonball, but most of the time they're just blowing in the wind.

Approximately 71% of the surface of the Earth is ocean — an area covering more than 139 million square miles. Despite their overwhelming size and the massive impact the oceans have on human life, more than 80% of Earth's ocean territory remains unmapped, unobserved, and unexplored.

Covering more than 63 million square miles of Earth's surface, the Pacific Ocean is by far the largest body of water on the planet. It is also the deepest, and its ocean basin contains more than half of the free water on our planet. All of the world's continents could comfortably fit inside the Pacific basin, which is also the oldest ocean basin on Earth.

In 2021, National Geographic officially recognized the Southern Ocean — surrounding the continent of Antarctica — as its own body of water, bringing the number of oceans in the world to five. The other four world oceans include the Atlantic, Pacific, Indian, and Arctic Oceans. The Southern Ocean is the only ocean to encircle a continent and touch three other oceans.