The ocean covers 70% of the Earth's surface and continues to entail some of the most mysterious creatures. Here are 7 facts you probably did not know about our oceans.

1. Two-thirds of all marine life remains unknown by scientists and society.

2. Not only are there species unknown, but there so are some sounds made beneath the surface.

There are a handful of sounds that researchers cannot explain with certainty. One specific one being "The Bloop" which mimics an iceberg cracking; however, scientists cannot identify it's source.

3. Underwater lakes and rivers exist on the ocean floor.

4. Coral reefs have developed their own form of sunscreen.

Corals in Australia's Great Barrier reef have created a protective barrier that blocks sun rays shining through the surface from harming them, according to the Commonwealth Scientific and Industrial Research Organization.

5. More historical artifacts lie on the ocean's surface than in all the history museums combined.

According to National Geographic, the ocean floor is home to more historical pieces than every history museum in the world. Treasures range from Viking sundials, jadeite gifts from gods, and ships from all over the world.

6. The longest range in the world, called the Mid-Oceanic Ridge, exists underwater.

7. We have more detailed maps of Mars than the ocean floor.

Because we've only explored about 5% of the ocean floor, most of remains such a mystery that our knowledge of it is much less than our knowledge of the surface of Mars!