Giant squid and sperm whale. Illustration of a giant squid (Architeuthis sp.) defending itself while being attacked by a sperm whale (Physeter macrocephalus). Sperm whales can reach 18 metres in length and giant squid can be up to 10 metres long. Sperm whales are toothed whales (teeth seen in lower jaw), though the teeth are thought to be used in aggression between males, rather than eating. Sperm whales dive deep (over 1000 metres) to hunt their main prey, giant squid. The squid can defend itself with suckers and sharp beak, and scars are found on whales from these defences. However, the giant squid is rarely seen, most often found in a sperm whale's intestines or washed up on a beach.