Sailing on a boat by yourself out at sea and out of sight of land can be exhilarating or terrifying, compelling or tedious – sometimes it can be all of these things just in one morning. It is an adventure at odds with our normal, sociable lives, carried out floating on a medium wholly inimical to our existence. But the deep ocean is also a remarkable place on which to think. Richard King’s engaging and curious book is about the debt we owe to solo sailors: women and men, young and old, who have set out alone. Spending weeks and months alone, slowly, quietly, and close to the ocean surface is to create the world’s largest laboratory: an endlessly changing, capricious and startling place in which to observe oneself, the weather, the stars and myriad sea creatures, from the tiniest to the most massive and threatening.