Using chromatophores in its skin, the squid can go from white to blue to gold in the blink of an eye. It can jet off at high speed by squirting water though its nozzle, or it can hover in one place with its fins. The cephalopods may not seem very closely related to the other mollusks, but physiologically, they are similar in internal construction. Perhaps the most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell. The octopods do not have shells at all, and the squid have a small chitinized internal shell.
Nautiluses are the only Cephalopods with an external shell.
Nautiluses are found in the South Pacific and Indian oceans. Cephalopods have the most well developed nervous systems of all mollusks, as well as the most well developed eye. The cephalopod eye is one of the most notable examples of convergent evolution in all of the animal world, because this eye evolved from a completely different direction than the mammalian eye, yet it turned out to function in almost the exact same way. Cephalopods, therefore, have extremely good eyesight. This eyesight is well suited for finding prey.