The giant squid (genus: Architeuthis) is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species. Giant squid can grow to a tremendous size: recent estimates put the maximum size at 13 metres (43 ft) for females and 10 metres (33 ft) for males from caudal fin to the tip of the two long tentacles (second only to the colossal squid at an estimated 14 metres (46 ft), one of the largest living organisms). The mantle is about 2 metres (6.6 ft) long (more for females, less for males), and the length of the squid excluding its tentacles is about 5 metres (16 ft). There have been claims reported of specimens of up to 20 metres (66 ft), but no animals of such size have been scientifically documented.
All squid move through the ocean using a jet of water forced out of the body by a siphon. They eat fish, other squid, and perhaps some argue, in the case of the largest species, whales. The legend of the Kraken, a many armed sea monster that could pull a whole ship under, may have been based on the giant squid.
(www.wikipedia.com)

"Recent research suggests that the squid are only aggressive while feeding."
(en.wikipedia.org/wiki/Humboldt_Squid)

The largest giant squid ever measured was discovered at Timble Tickle on November 2, 1878. Three fisherman were working not far off shore when they noticed a mass floating on the ocean they took to be wreckage. They investigated and found a giant squid had run aground. Using their anchor as a grappling hook they snagged the still living body and made it fast to a tree. When the tide went out the creature was left high and dry. When the animal died, the fishermen measured it and then chopped it up for dog meat. The body of the squid was twenty feet from tail to beak. The longer tentacles measured thirty five feet and were tipped with four inch suckers.

We know the giant squid tangles with whales from eye-witness accounts. In October 1966, two lighthouse keepers at Danger Point, South Africa, observed a baby southern right whale under attack from a giant squid. For an hour and a half the monster clung to the whale trying to drown it as the whale's mother watched helplessly. "The little whale could stay down for 10 to 12 minutes, then come up. It would just have enough time to spout - only two or three seconds - and then down again." The squid finally won and the baby whale was never seen again.

Giant Squid have been seen in battle with adult whales too. In 1965, a Soviet whaler watched a battle between a squid and a 40 ton sperm whale. In this case neither were victorious. The strangled whale was found floating in the sea with the squid's tentacles wrapped around the whale's throat. The squid's severed head was found in the whale's stomach.