This is an alien invasion story that pits humanity against creatures that take over the depths of the ocean and then proceed to attack. Less subtle than the Midwich Cuckoos, though stylisticly and technically exceedingly similar, this novel is told from the perspective of a journalist who accidentally gets caught up in events, but only as he looks back on them from a distance of time - making the protagonist very similar to that of The Midwich Cuckoos. Another similarity is the assertion that two intelligent species could not co-exist, but instead must come to strife. Again Wyndham's false understanding of evolution and ecology is put forward to justify this view.