Sound travels about 4.3 times faster in water than in air, allowing whale songs to carry for thousands of miles.

Dolphins can recognize themselves in mirrors.

Sea otters hold hands while sleeping so they don't drift apart.

Octopuses can solve simple puzzles and open jars.

Nostalgia was once classified as a medical disorder — Swiss physicians in the 17th century believed it was a brain disease.

Some prehistoric marine reptiles hunted in ancient oceans.

There are underwater lakes on Earth.

Some dolphins cooperate to herd fish while hunting.

Moose have large antlers used during mating season.