In The Width of the Sea, two intertwined families, the Fitzes and the Albins, struggle to survive on the Maine coast despite a dying fishing industry. At the seaport town of Rosaline, the sea may be wide, but it is now almost empty. Fishing boats known as "draggers" have long since scraped the ocean bottom clean "like so many hands to so many mouths."

Prospects are bleak. The processing plant has closed, fishing restrictions are on the increase, and the government is offering a 'buyback package' -- offering to pay fishermen to scuttle their boats and quit.

The elder Fitz, Warren, owns the fishing boat Pearl, and he has spent all his life either at sea or in the town bar. Fishing "kept him from dying of drink, and drinking kept him from dying of boredom." So attuned is he to his boat and the weight of his fishing net, he swears he can feel its drag. He would know a good catch by the "strain on the warps, a hum on the cables, a certain heaviness in his guts."

Warren's son John Fitz is angry with the old men for having taken all the fish, but befuddled by the realization that he "would have fished the same, if he'd been born thirty years earlier." He crews on the Pearl, along with his life-long friend Chris Albin, a drug addict.

John's high school sweetheart is Yve Albin, who also happens to be Chris's sister. Almost 30 and still living with her parents, she worries that the chance to marry and to have a child is drying up like the fishing industry, that she's at the end of everything - "living in the last little bit after the end. Like … that blue dot on the TV after you turn off the set, that small blip."

Chris Albin is married to a restless Kate, who tends bar at the town's gathering spot, the Whiskey Wind. Their young son Martin drifts between his grandparents and aunt Yve.

Some townspeople, Citizens Associated for Restorative Projects (CARP), look for ways to attract tourists and "yachties." They run a museum and a children's discovery center, where one exhibit is about Carp, a freshwater fish strangely unrelated to the town's history. Antagonizing the fishermen, CARP forces fishing boats off the town pier to make room for a tourist attraction, the restored 1902 schooner Shardon Rose.

With no option but to take the government buyback, Chris persuades John to sail the Pearl to Miquelon, off the coast of Newfoundland, and to run drugs back to the United States. Desperate and inexperienced, these young Maine fishermen initiate an astounding train of events for Rosaline and for the Fitzes and the Albins.