Dumbo octopuses live at depths of 3,000–4,000 meters and are named for ear-like fins they use to swim.

The Great Barrier Reef is the largest coral reef system in the world.

The ocean contains structures larger than mountain ranges.

The Portuguese man o' war's tentacles can extend up to 50 meters and remain dangerous even when detached.

Dolphins have been observed surfing ocean waves purely for fun — one of the clearest signs of play in non-human animals.

The Mediterranean Sea loses more water to evaporation than it gains from rivers, maintained by inflow from the Atlantic.

The Great Barrier Reef supports thousands of marine species.

Ancient oceans once covered much of Earth's surface.

The Atlantic Ocean is widening by about 2.5 cm per year as tectonic plates spread apart.