The world's largest marine protected area is the Ross Sea in Antarctica — covering 1.55 million square km.

Some coral reefs are visible from space.

The Mariana Trench is so deep that Mount Everest could be placed inside it and still be covered by over a mile of water.

The Mariana Trench is so deep that Mount Everest could be submerged in it with over a mile to spare.

Certain marine animals use camouflage to blend into coral reefs.

Deep-sea pressure at the Mariana Trench is over 1,000 times atmospheric pressure at sea level.

Some deep-sea octopuses brood their eggs for years.

The deep-ocean zone below 1,000 m is called the midnight zone — no sunlight reaches it.

Sea horses swim upright rather than horizontally.