The Kraken Wakes is an apocalyptic science fiction novel by John Wyndham, originally published by Michael Joseph in the UK in 1953 and first published in the US in the same year by Ballantine Books under the title Out of the Deeps as a mass market paperback. The title is a reference to Alfred Tennyson's sonnet The Kraken, which describes a Scandinavian sea monster.
The novel describes escalating phases of what appears to be an alien invasion; as told - with quite a bit of wry humour, even when describing manifestly non-humorous situations - through the eyes of Mike Watson, who works for the fictional EBC (English Broadcasting Company), and his wife and co-worker Phyllis. A major role is also played by Professor Andrew Bocker - more clear-minded and far-seeing about the developing crisis than everybody else, but with the talent of telling the public far more than they are capable of absorbing at a given moment.
In the first phase, objects from outer space land in the oceans. Mike and Phyllis happen to see one of the "meteors" falling into the sea, from the ship where are sailing on their honeymoon - an exciting moment for everyone on board, but nobody realizes that they have witnessed the beginning of an invasion from space. Eventually the distribution of the objects' landing points - always at ocean deeps, never on land - implies intelligence. (An intelligence which is, obviously, interested especially in ocean deeps.)
As repeatedly stated in the early parts, conflict was not inevitable. The aliens appear to come from a gas giant, and can only survive under conditions of extreme pressures in which humans would be instantly crushed. The most deep parts of the oceans are the only parts of Earth in any way useful to them, and they have no need or use for the dry land or even the more shallow parts of the seas. In theory, the two species could have co-existed indefinitely, hardly noticing each other's presence.
However, humans are nevertheless disturbed and feeling threatened by this new phenomenon on their world - particularly since the newcomers show signs of intensive work to adapt the ocean deeps to their needs, and there are even indications of their digging a tunnel deep underground to connect the Atlantic and the Pacific, in effect their own version of the Panama Canal.
A British bathysphere is sent down to investigate, and is destroyed by the aliens. The UK government reacts rashly and rather unwisely - as remarked by protagonists at the time - by exploding a nuclear device on the spot, under the guise of "testing" it (an act not yet forbidden, at the time of writing, by the Test Ban Treaty).
While the aliens in this specific deep are destroyed, their fellows at many other places survive - and come to see the humans as a threat to be eliminated. And as soon turns out, they have many more means of getting at the humans than the other way around. Moreover, humanity is not united in the face of the mounting threat - the Cold War between West and East is at its height, with the two sides often suspiciously attributing the effects of the alien attacks to their human opponents.
Phase two of the war starts with ships being attacked, causing havoc to world shipping, and the British are humbled to realize "how easily we have been driven off the oceans" (the book was written at the time when, in real life, they had to get used to no longer being an empire). Shortly after, the aliens start 'harvesting' the land by sending up 'sea tanks' which capture humans from seaside settlements; this is presumed to be for investigation, although the humans always drown. However, humans manage to overcome this phase.
Phase Three: The aliens begin melting the ice caps, causing sea levels to rise. London and other ports are gradually flooded, causing widespread social and political collapse - the same happening in many other countries (there is mention of the Netherlands disappearing under the rising sea, with the terrified Dutch fleeing after realizing that they had "lost their centuries-old struggle with the sea").
The story follows the journalist couple Mike and Phyllis Watson, as they cover this this story of the alien attacks for the English Broadcasting Company - which they do until the radio (and organized British social and political life in general) cease to exist - whereupon they can only try to survive and understand what is going on.
At the end, humanity (specifically, the Japanese) develops an underwater ultrasonic weapon that kills the aliens. However, the world population has been reduced to less than a fifth of its level before these events.
Throughout the book the menace (assumed aliens) remains concealed and virtually unseen; everything we know about them is inferred from their actions. The most which is learned is that, once they have been killed, "large masses of organic jelly" float to the surface of the sea.
The main criticism which has been made is that it is in places a re-hash of some ideas from Wyndham's first major novel, The Day of the Triffids. The ending is considered weak as well, suggesting that the author was not sure how to conclude the novel.
The novel contains what is, in a way, Wyndham's starkest statement of his assumption that two intelligences must necessarily fight each other to the death, although he implies this in The Chrysalids and The Midwich Cuckoos as well.