An Unexplored Territory
More than 70 percent of the Earth's surface is covered by ocean, but to date,we've explored less than 5 percent of it.
Geophysicist Walter Smith, with the National Oceanic and Atmospheric Administration's Laboratory for Satellite Altimetry clarified the situation that 90% of the ocean floor is unmapped;
"If you make an estimate using all the historical data in a place like South Pacific, and compare it to the United States at the same scale, it looks a bit like the interstate highway system," he explained.
"It's like sending surveyors out and saying that every few miles they can measure the height of the ground, but [they can] never leave the interstate highway system—then asking them to come back and make a map showing all the geographic features of the United States."

The Kraken
But men have seen such creatures, and indeed been devoured by them. The exigencies of the Second World War took ships to waters round the globe which are otherwise seldom frequented. Lieutenants Rolandson, Davidson RN and Lieutenant R E Grimani Cox of the Indian Army, were caught by a German raider flying the Japanese flag in a remote part of the South Atlantic. After firing on the ship til she caught fire, the raider gave all aboard five minutes to take to the boats. The three officers found themselves left with a small raft and nine companions, taking turns to cling to the raft or sit upon it.
They were faced with all the traditional nightmares of the ship-wrecked; a burning sun, a terrible thirst, attacks from Portuguese men-of-war, which Lieutenant Cox said 'stung like a million bees', and then, on the third day, the sharks appeared to pick off the wounded and those who had gone mad with thirst. After three more days, the sharks suddenly disappeared - not a relief but a prelude to the most appalling moment of all. Slowly, beside the raft, a gigantic shape appeared with huge tentacles. For some time it seemed to stand off and contemplate its strategy. Then, deliberately, it reached out onto the raft and grabbed one of the Indian survivors 'hugging him like a bear'. Cox and the others made a futile attempt to tear the tentacles away, Cox himself suffering several sucker wounds, but the creature slowly took the Indian away. Apparently one man sufficed, for Cox and the two navy officers, picked up by a Spanish ship, lived to tell the tale.
Arthur C Clarke's Mysterious World (paperback, 1980 Fontana Press, London) p106-107.

Originally posted by Frogs
Don't forget the one Monster Quest got a short vid of one when they put a camera on a humbolt squid..

Monster Quest - Giant Squid

How big can a squid get? Estimates based on peices of carcasses found in the belly's of sperm whales range up to one hundred feet. One unconfirmed story, though, suggests they might get even larger. One night during World War II a British Admiralty trawler was lying off the Maldive Islands in the Indian Ocean. One of the crew, A. G. Starkey, was up on deck, alone, fishing, when he saw something in the water:

"As I gazed, fascinated, a circle of green light glowed in my area of illumination. This green unwinking orb I suddenly realized was an eye. The surface of the water undulated with some strange disturbance. Gradually I realized that I was gazing at almost point-black range at a huge squid." Starkey walked the length the of the ship finding the tail at one end and the tentacles at the other. The ship was over one hundred and seventy five feet long.