In pictures: The fascinating, unique octopus

The southern keeled octopus, found in the shallow coastal waters of south-eastern Australia, often hides in the sand.

Capricorn night octopuses are nocturnal.

The blue-ringed octopus is small and beautiful, but its colors say "danger," since it's highly venomous.

The Capricorn night octopus, found mainly in the waters off Australia, emerges at night to forage.

This pale octopus, a native of Australia, is about 4.5 inches long.

The East Pacific red octopus is widely found on the West Coast of the United States.

This octopus has just emerged from its larval stage.

The Atlantic pygmy octopus is quite tiny; this specimen's mantle is just over an inch long.

This female octopus, a species yet to be scientifically described, is tending her eggs.

The California two-spot octopus, also called the bimac octopus, is a species divers come across often, since they live in relatively shallow waters, about 65 feet.

Plain body octopuses live in dens at the base of corals, pulling in pieces of dead coral to block the entrances during the day.

The wonderpus octopus is so called because of the striking patterns on its long, thin, arms.

This juvenile day octopus could grow to be about 30 inches across.

The star-sucker pygmy octopus is the smallest known octopus at under an inch long.

Because the day octopus feeds during the day, it has exceptional camouflage abilities.

The algae octopus's resting camouflage makes it look like a shell covered in green algae.