Cuttlefish are shallow water dwelling cephalopods. They are typically found near the coastlines of the Mediterranean, Baltic and North Seas, as these locations have the temperate waters in which cuttlefish are most comfortable. Cuttlefish are smaller than their fellow cephalopods the octopuses, averaging 20 to 30 cm when fully grown. Cuttlefish are masters of camouflage as their skin can change colors in order to hide from predators or sneak up on prey.
One of the most notorious cephalopods is the octopus. Octopuses have high brain to body ratios, and their large brain and problem solving ability have caused them to be regarded as very intelligent marine creatures by the scientific community. Octopuses can vary from the size of a penny to 10 feet long, depending on the species. They are found in oceans throughout the world at varying depths. Octopuses are known for their ink sacs, which expel ink as a defense mechanism when the octopus feels threatened. They have very sharp vision; however, they are color blind. Octopuses grab onto prey with their tentacles and draw the prey into their beaks, where it is devoured.
Squid have long, lean bodies that are similar in shape to those of cuttlefish. Different species of squid prefer different water temperatures and salinities, though the majority of squid species can be found in the North Atlantic. Squid tend to grow to about 24 inches, though some species, like the colossal squid, grow much larger. Squid have two large tentacles that are used as predatory weapons, in the same way that octopuses use their tentacles.
The colossal squid is one of the largest cephalopods. Though few specimens have been studied, reports of its measurements make it larger than the giant squid, at up to 45 feet in length, according to MarineBio.org. In general, squid have large eyes; the colossal squid, however, has what are considered to be the largest eyes of all animals, which helps account for its excellent vision. Colossal squid reside in cold waters near the Antarctic at ocean depths greater than 3000 feet. Therefore, their large eyes are useful hunting tools in the dark waters of the Antarctic.