In Life at Sea, anthropologist Monique Layton draws on her experiences on modern cruise ships to examine the evolution of sailing from the Age of Exploration to the Age of Tourism. Using historical records and the reports of people who once went to sea through necessity, curiosity, or adventure, she shows the common events that have shaped their voyages and the ingenuity, courage, and determination that characterize mankind's connection with the all-surrounding sea.

The book's topics range from the dependence on the wind and manpower through the invention of devices to determine location at sea to modern maritime technology, from the devastation of scurvy and starvation on early ships of exploration and trade to the luxuries of omnipresent food, on-board medical treatment, and professional entertainment available on behemoth cruise ships.

The book also delves into the deeper meaning of seafarers' rituals and their harsh lives with severe discipline and few rewards. These aspects along with the horrors of the slave trade and naval warfare, the harrowing crossings of emigrants and convicts, the ambiguities of piracy, and economics of global trade all show the contradictory elements that have consistently shaped travel by sea.