It is in the phylum mollusca which includes snails, clams and other shelled bivalves, and of course octupi and squids. It is in the class cephalopoda. Instead of having a foot like the rest of the molluscs they have tentacles. Nearly all cephalopods are carnivores and squids in particular are very voracious predators. Many cephalopods use venomous secretions to speed up th e death of their prey.
Cephalopods use jet propulsion for locomotion.
Water is forced out their body through a siphon creating their propulsion. This propulsion system is ineffiecient so for the most part squid and octopus are slow. They are the only class of molluscs that have a closed circulatory system, they have this because of a great demand for oxygen. They also have a very developed nervous system having extremely large nerve fibers which enables them to respond very quickly in the precense of danger or a food source. It is the biggest eye in the animal kingdom.