How Much of the Ocean Has Been Explored? Shockingly Little!

scuba diver exploring an underwater cave in a tropical coral reef. — Although we've come a long way with space exploration, we have a long way to go with ocean exploration. Jason Edwards/Getty Images

Oceans make up about 71 percent of Earth's surface. They're immensely important to the health of Earth and those of us who inhabit it. There are five main oceans: the Atlantic Ocean, Pacific Ocean, Indian Ocean, Arctic Ocean and Southern Ocean, so when we say the "world's ocean" or "the ocean," we are referring to all these ocean basins together.

The ocean drives weather patterns, regulates temperature and ultimately supports all living organisms. It's been a vital source of sustenance, transportation and commerce throughout history.

Yet, just 5 percent of the global ocean has been explored and less than 10 percent has been mapped using modern sonar technology. If we can send satellites millions of miles into space, then why has so much of the ocean's wild frontier been left unmapped, unobserved and unexplored?

Well, it's complicated.

Why Has So Little of the Ocean Been Explored?

remotely operated vehicles underwater — ROVs (remotely operated vehicles) are very useful in the exploration of the deep ocean floor without the need to send divers who might be subject to risk. ROVs rely on ocean currents to carry them along.
Humberto Ramirez/Getty Images

First, there's a lot more to the ocean than meets the eye. We've always been able to explore the ocean's surface. But we've only just started looking into the ocean depths and sea floors within the past few decades. Satellites have helped us chart the ocean's surface temperatures, waters and colors (which can indicate plant life). More advanced technology is needed to dig deeper, so to speak. Submarines and sonars have helped with that.

But when you reach the deep ocean about 650 feet (200 meters) or more below the water's surface, you leave the so-called "sunlight zone" and enter complete darkness. At these great depths, you lose all visibility. It's also extremely cold and the pressure is body-crushing.

For perspective, at sea level, the pressure on your body is about 15 pounds per square inch (103.42 kilopascals). If you float above Earth's atmosphere into space, your body pressure decreases to zero. But if you drop deep into the ocean's depths, that pressure increases the deeper you go. If you were to go to the bottom of the Mariana Trench — the deepest part of the ocean, about 7 miles (11.2 kilometers) deep — you would feel about 1,000 times more pressure than what you would feel on the surface or the equivalent of about 50 jumbo jets pressing down on your body.

As you can see, deep sea exploration is tough. But there is still hope to learn more. Agencies such as the National Oceanic Atmospheric Administration (NOAA) are leading efforts in ocean exploration by supporting expeditions to investigate and document unknown and little-known regions.

It's difficult to protect our ocean if we know so little about it. And there are countless reasons why we should protect it. The ocean produces more than half of the world's oxygen. It also helps regulate weather patterns, provides food and medicine and bolsters trade among nations around the globe.