The Last Wave follows the life of Martha, a woman who has swum the English Channel ten times, and the complex relationships she has with her husband, her children, and her close friends. The one constant in Martha's life is the sea, from her first accidental baptism to her final crossing of the channel. The sea is an escape from her responsibilities as a wife and a mother; it consoles her when she is diagnosed with cancer; and it comforts her when her husband's mind begins to unravel.