The novel describes the course of an attack on humanity by creatures from the ocean depths, as told through the eyes of two characters: Mike Watson, a journalist for the English Broadcasting Company (EBC) with his wife and colleague Phyllis; and Professor Alastair Bocker, who is more clear-minded and far-sighted about the developing crisis than everybody else but who often alienates people by telling brutally unvarnished and unwanted truths. Mike and Phyllis are witness to several events of the invasion, which proceeds in drawn-out phases; it takes years before the bulk of humanity even realises that the world has been invaded. In the first phase, objects from
outer space land in the oceans. Mike and Phyllis happen to see five of the "fireballs" falling into the sea, from the ship where they are sailing on their honeymoon. Eventually the distribution of the objects' landing points – always at ocean depths, never on land – implies intelligence. The aliens are speculated to come from a
gas giant and thus can only survive under conditions of extreme pressure in which humans would be instantly crushed. The deepest parts of the oceans are the only parts of Earth in any way useful to them and they presumably have no need or use for dry land or even the shallower parts of the sea. Bocker puts forward the theory that the two species could co-exist, hardly noticing each other's presence. Humanity nevertheless feels threatened by this new phenomenon, particularly since the aliens show signs of intensive work to adapt the ocean deeps to their needs. A British
bathysphere is sent down to investigate and is destroyed by the aliens with the loss of two lives. The British government responds by exploding a nuclear device in the same location. The aliens' technology proves formidable, and an American attempt to use a nuclear bomb ends in disaster. Ships all over the world begin to be attacked by unknown weapons and in each case are rapidly sunk, causing havoc to the world economy. Humanity is not united in the face of the threat because of the ongoing
Cold War, with the two sides often attributing the effects of the alien attacks to their human opponents or refusing to co-operate because of differing political ideals and mutual distrust. Phase two of the war starts when the aliens start "harvesting" the land by sending up "sea tanks", using mutated and genetically altered sea creatures, which capture humans from coastal settlements. Like much of what the aliens do, the reasons for these attacks are inscrutable. The Watsons witness one of these assaults on a
Caribbean island. Eventually coastal settlements establish such defences against these "sea tank" raids that they become far less frequent, but this only happens after raids are experienced on every continent. In the final phase, the aliens begin melting the polar
ice caps, causing the sea level to rise. London and other ports are flooded, causing widespread
societal collapse. The Watsons cover the story for the EBC until the radio (and human civilisation in general) ceases to exist, whereupon they can only escape to a Cornish holiday cottage which, due to the floods, now exists on an island. Ultimately, scientists in Japan develop an underwater
ultrasonic weapon that kills the aliens. The human population has been reduced to between a fifth and an eighth of its pre-invasion level and the world's climate has been significantly changed, with water levels 120 feet higher than before.
Plot narrative Even at the end, humans have no clear idea what the aliens looked like. The most they have is some
protoplasm that floated to the surface of the sea after the ultrasound weapon was used. As the protagonist states in the book, the book aims to demonstrate that an alien invasion of Earth could take a very different form from that in
The War of the Worlds; publication of the book coincided with the release of the 1953 film
The War of the Worlds, an adaptation of
H. G. Wells' classic work, which was both a critical and
box office success.
Plot differences Depending on the book's printed origin there are several changes to the plot: • The US edition, entitled
Out of the Deeps, cuts almost an entire chapter found in the UK edition on how the Watsons gained possession of
The Midge yacht, and their aborted attempt to use a dinghy to get to Cornwall. It simply states that Freddie Whittier "found it" one day. • The US edition skips several paragraphs detailing Mike Watson's mental state and his several subconscious attempts to commit suicide, with only Phyllis preventing his success. Instead, the US edition just states that Mike goes on holiday. • In the US epilogue, the Watsons are tracked down by Bocker via helicopter and he explains a great deal of what has happened to the world while Mike and Phyllis have been isolated – even describing the Japanese ultrasonic device in some detail. In the UK edition they are instead approached by a neighbour in a sailboat, who gives them only a brief overview of what has happened in the world – excluding much of the detail and just mentioning that the Japanese have developed an ultrasonic device that is lethal in the depths of the sea. He tells them that their names have been broadcast on radio as important people whom the new "Council For Reconstruction" is wanting to locate and employ. • The UK edition is less bleak than the US version, implying that humanity has already begun to rebuild and that civilisation survives – albeit at a lesser level than before. • There are several changes for a US audience in terms of language and phraseology. Overall, the U.S. edition is significantly shorter. ==Reception==