If you took all the water in all of Earth’s ocean and filled up as many bathtubs as you could, then put those bathtubs end-to-end, you’d be able to make a line of bathtubs all the way to the Moon. And back. And back to the Moon. And back to Earth…until you had 5 round trips between the Earth and the Moon!

The ocean actually gets most of its salt from rivers, which wash away tiny amounts of salt from river beds as they run towards the sea. So, does that mean the ocean is getting saltier? No - because the ocean is also constantly losing salt to sea spray, making salty deposits like salt flats, and other ways.

The waves you play in at the beach aren’t caused by the Moon, as many people believe. They’re actually caused by wind. Wind blowing over the ocean’s surface for miles and miles can eventually ruffle it enough to push it. That pushed water pushes other water, which pushes other water - in other words, a wave. That wave of energy travels until it’s interrupted, usually by land, which means that the waves you’re swimming in may have originated on the other side of the world.

The bottom of the ocean is a little over 2 miles (3.6 km), for the majority of the ocean. It slopes downward as you get farther out from land before bottoming out. However, there are deep trenches in the ocean floor which can go down much farther. The deepest of these trenches yet discovered is the Marianas Trench, located near the island of Guam, and the deepest part of the Marianas Trench is the Challenger Deep, which is nearly 7 miles deep - so deep, that if you put Mt. Everest at the bottom, the summit would still be over a mile underneath the surface.

The Siphonophore might be the longest creature ever seen. Scientists found one that was 150 feet (46 m) long - half the length of a football field! These strange creatures live deep under the surface, and are as thin as a broomstick. They emit a beautiful, eerie glow, like fireflies, and are actually a colony of thousands of teeny tiny creatures called zooids. The second-longest animal is the lion’s mane jellyfish, which has tentacles up to 120 feet (36 m) long.

The octopus is one of the quickest color-changers in the animal kingdom - it can change colors faster than the blink of an eye. By comparison, a chameleon can take over a minute to change color completely. Octopi can also change the actual texture of their skin in order to blend in to their environment, making them masters of disguise. They do it by inflating tiny balloon-like cells in their skin called chromatophores. Octopi fill each chromatophore with a different-colored pigment, sort of like the pixels in your TV.

The vast majority of the ocean remains unexplored. Over 80% of the ocean has never been mapped, explored, or even seen by humans. That means there’s lots and lots of unexplored ocean, with creatures left to discover - maybe by you!

The ocean floor is mapped primarily by using sonar - bouncing sound waves off the bottom of the ocean and measuring how long they take to come back, to figure out how far away it is. Despite technological advances, we’ve still only mapped about 1/20th of the ocean’s floor. So the deepest part of the ocean, the Challenger Deep, may not actually be the deepest part we’ll ever discover.