Earth's longest chain of mountains, the Mid-Ocean Ridge, is almost entirely beneath the ocean, stretching across a distance of 65,000 kilometres. It's said that this mountain chain is less explored than the surface of Venus or Mars.

There are three different types of coral reef formations—barrier reefs, coral atolls, and fringing reefs. Barrier reefs help to protect lagoons and other types of shallow water, coral atolls (which are often mistaken for islands) are made from volcanic remains, and fringing reefs are found right along the coastline.

There's around 20 million tons of gold dispersed throughout the oceans. It is, however, diluted pretty much to a pulp—its concentration is only a few parts per trillion, according to the National Ocean Service. The ocean floor also has undissolved gold embedded in it, but it's not cost-effective to mine it. However, if the ocean's gold were equally distributed among every person on earth, we'd each receive nine pounds of gold.

Giant kelp can live up to seven years. Factors such as the severity of winter storms may affect its life span. Its average growth (in spring) is 27 cm/day (~10 inches/day), yet it may grow up to 61 cm/day (2 ft/day).

The Largest Deep Sea Fish Is Called Greenland Shark, which has a length of 6.4 meters. Often mistaken for Great White Sharks because of their massive size, they reach up to 24 feet (7.2 meter) in length and weigh up to 3,100 lbs (1,400 kg). Greenland Sharks have a voracious appetite and will eat almost anything. Typically they eat eels, lumpfish, flounder, and other small sharks, but they will also eat carrion, the meat of dead animals. They have also been known to eat land animals. Greenland Sharks have been found with a polar bear jaw, an entire reindeer, horse bones, and a moose hide in their stomachs. Greenland Sharks are rarely observed in the wild. It wasn't until 1995 that scientists were able to capture the first pictures of a Greenland Shark swimming in its natural habitat.

Fish use a variety of low-pitched sounds to convey messages to each other. They moan, grunt, croak, boom, hiss, whistle, creak, shriek, and wail. They rattle their bones and gnash their teeth. However, fish do not have vocal chords. They use other parts of their bodies to make noises, such as vibrating muscles against their swim bladder.

The harp sponge captures their prey, such as copepods and other crustaceans, with the velcro-like hooks on their external body surfaces. Once the hooks have ensnared the sponge's prey, it secretes a digestive membrane that surrounds and engulfs the captured prey, breaking it down until the sponge can absorb it through its pores. Terrifying and beautiful at the same time.

Fish have sleep-like periods where they have lowered response to stimuli, slowed physical activity, and reduced metabolism but they do not share the same changes in brain waves as humans do when they sleep.

Many anglers believe that pike lose their teeth in the summer and don't bite. In fact, both pike and muskies continually shed old teeth and grow new ones. While it's true that pike fishing often gets tough during the summer months, the poor bite is probably related to a glut of baitfish or the fact that pike often move into deeper, cooler water as the summer progresses.

It turns out, humans aren't the only creatures in need of a winter vacation. In 2002, scientists discovered an area in a remote part of the Pacific Ocean, partway between Baja California and Hawaii, where typically coastal great white sharks will migrate to in the winter. The scientists named the spot the White Shark Café and some sharks hang around the area for months before heading back to the coast for warmer weather.