Below the thunders of the upper deep;
Far far beneath in the abysmal sea,
His ancient, dreamless, uninvaded sleep
The Kraken sleepeth: faintest sunlights flee
About his shadowy sides; above him swell
Huge sponges of millennial growth and height;
And far away into the sickly light,
From many a wondrous grot and secret cell
Unnumber'd and enormous polypi
Winnow with giant arms the slumbering green.
There hath he lain for ages, and will lie
Battening upon huge seaworms in his sleep,
Until the latter fire shall heat the deep;
Then once by man and angels to be seen,
In roaring he shall rise and on the surface die.
The Kraken is also closely associated with Leviathan, referenced twice in the Bible (in the Book of Job and in Revelations) as a huge and otherwise unspecified sea-monster who is currently sleeping, but who will rise in wrath at the End of Days. Leviathan, by context in the Bible, is thought of by its authors as batting for the other side, although Anthony Crowley might point out that not everything has to have a side, and just because he/she/it isn't on your payroll doesn't necessarily mean he/she/it has to be on ours.
Leviathan might be thought of as being on the side of all those greater and lesser sea creatures, who are harvested by Japanese factory ships as part of an ongoing scientific experiment into how many portions of sushi you can get out of endangered whale species. (Naturally, all valid scientific experiments have to be repeatable, and the Japanese are keen on ensuring the validity of the research). Leviathan awakes in Good Omens, as is mandated in the script for the Last Days, to wreak revenge on at least one Japanese fishery ship.
Leviathan - as a huge, unstoppable, inadvertently destructive but intelligent sea monster - is also a character in Robert Shea and Robert Anton Wilson's Illuminatus! series of novels. Interestingly enough, in The Science of Discworld, the Dean devises a marine life-form guaranteed to survive anything the Universe can throw at Roundworld which shares many aspects of Shea and Wilson's conception of Leviathan...
In "Real Life" (well, for a given value of real), the Bloop is the name given to an ultra-low frequency underwater sound detected by the U.S. National Oceanic and Atmospheric Administration several times during the summer of 1997. The source of the sound remains unknown.
The sound, traced to somewhere around 50° S 100° W (South American southwest coast), was detected repeatedly by the Equatorial Pacific Ocean autonomous hydrophone array, which uses U.S. Navy equipment originally designed to detect Soviet submarines. According to the NOAA description, it "rises rapidly in frequency over about one minute and was of sufficient amplitude to be heard on multiple sensors, at a range of over 5,000 km." Though it matches the audio profile of a living creature, there is no known animal that could have produced the sound. If it is an animal, it would have to be, reportedly, much larger than even a Blue Whale, according to scientists who have studied the phenomenon. Could it be a Kraken...?