Oceans of the world: 90 percent is still unmapped | Photo: Shutterstock

World Ocean Day is celebrated every year on June 8. So, what should we know about the body of saline water that covers two-thirds of the planet's surface?

Earth is the only planet that is known to have large, stable bodies of liquid water on its surface. Oceans generate most of the oxygen we breathe, and they regulate our climate.

Oceans clean the water we drink and offer a pharmacopeia of potential medicines.

The Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans cover approximately 72 percent of the planet's surface.

Oceans are the habitat of at least 230,000 known species.

The volume of the world's oceans can be thought of as a cube of water with an edge length of 1,111 kilometers (690 miles).

Their average depth is 3,790 meters (12,430 feet), and their maximum depth is 10,923 meters (6.787 miles).

The deepest point in the ocean is the Mariana Trench, located in the Pacific Ocean.

In 1960, the Trieste, manned by a crew of two men, successfully reached the bottom of the trench.

The ocean is blue because water absorbs colors in the red part of the light spectrum.

Like a filter, this leaves behind colors in the blue part of the light spectrum for us to see - nevertheless, dissolved organic matter and chlorophyll help to color it blue.

Take a look at the following facts and figures about the oceans of the world:

1. Life began in the ocean 3.1 billion to 3.4 billion years ago;

2. Hardly any light penetrates deeper than 200 meters (656 feet), and no light penetrates deeper than 1,000 meters (3,280 feet);

3. Two-thirds of all marine life remain unidentified;

4. 90 percent of the ocean is still unmapped;

5. The Earth's longest mountain range is underwater;

6. 80 percent of sharks are unable to hurt humans;

7. Between 50 and 80 percent of all life on Earth is in the oceans;

8. 97 percent of the Earth's water is in the oceans;

9. 90 percent of all volcanic activity occurs in the oceans;

10. The highest tides in the world are at the Bay of Fundy;

11. The pressure at the deepest point in the ocean is more than 11,318 tons per square meter (the equivalent of one person trying to support 50 jumbo jets);

12. The largest tsunami of all time measured 60 meters above sea level;

13. The Pacific Ocean, the world's largest ocean, contains about 25,000 islands;

14. If all the world's ice melted, the oceans would rise 66 meters;

15. The average temperature of the ocean water surface is about 62.6 °F (17 °C);

16. Antarctica has as much ice as the Atlantic Ocean has water;

17. Three times as much rubbish is dumped into the oceans as the weight of fish caught every year;

18. Blue whales are the largest animals on our planet ever;

19. The Great Barrier Reef is the largest living structure on Earth;

20. 39 percent of US citizens live in shoreline counties;

21. The National Aeronautics and Space Administration (NASA) has revealed that the seas of the world have risen three inches (eight centimeters) since 1992. Data suggests that the sea level will likely increase by one meter or more in the next 100-200 years;

22. A report by the Ellen MacArthur Foundation concluded that by 2050, oceans will contain more weight plastics than fish. Researchers believe that by 2050, the entire plastics industry will consume 20 percent of the world's oil production and 15 percent of the annual carbon budget;

Discover the best sea and ocean quotes of all time.

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