Tom Crick, fifty-two years old, has been history master for some thirty years in a private secondary school in Greenwich, a point of zero degrees longitude, in a sense the place where, in a world that sets its clocks according to Greenwich Mean Time, time begins. Tom’s wife, Mary, also in her early fifties, has been married to Tom for as long as he has been teaching. Until shortly before the immediate action of the story, she has been working with the elderly in a home. She has given up that job.
The students in Tom’s school have grown increasingly scientifically oriented, and the headmaster, Lewis Scott, himself a physicist, has little sympathy for Tom’s subject, a fact that he in no way masks. One of Tom’s students, Price, an intelligent sixteen-year-old whose father is a mechanic, presses Tom with questions about the relevance of learning about such historical events as the French Revolution. The youth’s skepticism causes Tom to change his teaching approach from one of presenting historical facts to one that involves his telling tales drawn from his own recollection. By doing so, he makes himself a part of the history he is teaching, relating his tales to local history and genealogy.
The headmaster has no sympathy for Tom’s new approach, even though it rekindles student interest in history. The headmaster tries to entice Tom into taking an early retirement at a decent pension. Tom resists because his leaving would mean that the History Department would cease to exist and history would simply be combined with the broader area of General Studies.
Finally, Tom’s hand is forced because his wife is arrested for stealing a baby from a shopping cart outside a market. She testifies that God told her to do it. The publicity that attends her arrest reflects badly on the school, and Tom is told that he now must go into retirement. He is given no alternative.
This is the bare frame of a story that becomes extremely complicated and convoluted. Tom uses his impending forced retirement as an excuse to unfold an extremely interesting story to his students. The bulk of Waterland is devoted to this story that, before it is done, covers some three hundred years of local history and relates it to the broader historical currents of those three centuries. Tom even makes occasional brief excursions to Anglo-Saxon times in telling his tales.
The primary plot of the story has to do with Tom’s relationship to Mary both before and after their marriage. She is reared on a farm close to where Tom’s father, a lock-keeper, lives with his two sons in the lock-keeper’s cottage. His wife dies when Tom is eight years old. Mary is also reared by her father because her mother died giving birth to her. Her father, remaining faithful to his wife’s memory, has not remarried. He sees that his daughter receives strict religious training and that she attends a good church school.
As Mary matures, her interest in men grows, and she and Tom slip into an affair. It is discovered that Mary is pregnant. Tom’s brother Dick asks Mary if he is the father of the child. Mary says that he is not and lies to him, telling him that sixteen-year-old Freddie Parr is the father, although she has not had an affair with Freddie. Dick, distraught at this information, struggles with the drunken Freddie, who cannot swim, and pushes him into the River Leem. He drowns. It is Tom’s father who pulls Freddie from the sluice in the deep of night, not realizing that his drowning is anything but accidental, as the coroner’s inquest finally declares.
Mary tries to provoke a miscarriage but fails, so she and Tom, the father of the child, go to Mary Clay, an old crone, who performs an abortion that leaves Mary sterile. Her father forces her into seclusion, and for three years she remains isolated, engaging largely in prayer and meditation.
Tom is away fighting in World War II. Finally the two fathers agree to bring their children together again; unknown to them, Tom has already written to Mary. When he comes home, the two marry, and Tom begins his teaching career, while Mary takes a position in an old persons’ home. They live thus for more than thirty years; then Mary gives up her job and becomes actively involved in the church. Finally, she steals a baby because "God tells her to." She explains the new arrival to Tom by saying that it is a gift from God. Obviously demented and obviously suffering from a pain that has been festering since her teenage abortion, Mary is arrested. Tom, as recounted above, is forced into an early retirement as a result of this disgrace.
A secondary plot involves the Atkinson family, which has run a brewery for many generations. Tom’s mother was an Atkinson. This subplot is interwoven intricately into the development and resolution of the primary plot.