Sperm whales are dedicated carnivores, whose diet is essentially comprised of all meat from various oceanic animals. Around 80 percent of the sperm whale's diet is made up of giant squid, with the remaining 20 percent an eclectic mix of fish, crustaceans and sharks. While the sperm whale's diet can be established with some certainty by examining its stomach contents, the animal hunts at extreme depths and as such (as of 2014), its encounters with giant squid have never been directly observed.
Sperm whales dive deep for their food. Female sperm whales are known to dive down to a kilometer under the surface, and males dive deeper still in search of prey. They can remain submerged for up to an hour while they hunt. Sunlight doesn't penetrate the depth at which sperm whales hunt, so they probably don't use their disproportionately small eyes. They do, however, have a keen sense of echolocation that works to isolate prey animals in total darkness. Blind yet healthy sperm whales have been captured, which suggests that eyesight is of secondary importance to the whales in gathering food.
While the hunting behavior of sperm whales has never been observed directly, many whales have been caught or beached with large circular scars on their bodies. This implies that the squid they eat struggle and fight to the death.