One hundred twenty thousand miles. Thirty thousand trips. Forty years. But just one captain. Like the U.S. Postal Service, the sailboat Endeavor has persevered through snow, rain, heat and gloom of night to become a constant fixture on the Nantucket waterfront. Running four trips every day for the last forty summers, Captain Jim Genthner has seen the island evolve from his slip on Straight Wharf. But once he throws off his bowlines and catches the fair winds out of the boat basin, Genthner reconnects with the timelessness of sailing on Nantucket that he found serendipitously forty years ago.

On a late fall day in 1981, twenty-seven-year-old Jim Genthner wandered up the cobblestones of Main Street in search of ice cream. He had just sailed to Nantucket with his brother Charlie and their family from Fairhaven, Massachusetts, aboard the Endeavor, a thirty-one-foot sailboat that Jim had spent two years constructing by hand in his parents’ backyard. When the two brothers reached the ice cream parlor, they were shocked by how expensive two scoops and a cone cost. Charlie turned to Jim and declared that the island was the perfect place for him to launch his charter sailing business. Now, forty-one years later, with its American flag snapping in the wind off its thirty-foot mast, Genthner’s Endeavor has become a quintessential part of the Nantucket experience.

Jim first learned to sail as a boy aboard a single-mast Sailfish at his family’s rustic compound in Lakeville, Massachusetts. With the help of his father, Jim constructed the Endeavor piece by painstaking piece, from the five thousand pounds of lead that made up her keel (installed by hand, in twenty-pound ingots) to the teak deck sourced from rummaging through endless piles of lumber in a Fall River, Massachusetts, warehouse. Spurred on by his love of sailing, Jim turned his passion into a profession by offering one-and-a-half-hour cruises to tourists four times each day on Nantucket.

A big part of its success was thanks to the hiring of one essential staff member. Sue Joseph was a college student who followed her roommate to Nantucket in search of a summer job. Never having been to the island before, she quickly befriended Jim and offered to give him a hand with his business. They married in 1987. Over the years, Sue has managed the “desk” side of operations (reservations, bookkeeping, in addition to raising their two children) from slip 1015 on Straight Wharf, while Jim takes fourteen eager passengers out onto Nantucket Sound several times a day each and every summer.

“This is such a story of survival,” Sue says, in between phone calls for Endeavor bookings as she stands in the warm morning sun on Straight Wharf. “The boat is such an extension of Jim. You can’t separate the man from the boat. It’s like somebody would ride a horse; he knows every movement, every motion, and it’s where he’s most comfortable.”

While sailing on the Endeavor, it’s easy to see that comfort level. Jim stands to see and navigate the busy harbor boat traffic while steering with his feet, the toe of his shoe lightly tugging at the very same wheel his mother gave him for Christmas so many years ago when he was still putting the boat together piece by piece. With Jim at the helm, the Endeavor has served as an informal floating classroom of sorts, not only for the passengers who freely ask him about everything from the ecology of the harbor to the who’s who of the superyachts moored there, but also to the two crew members they hire every summer, typically college students who find a mentor in the old captain.

This summer, however, it’s a family affair, with their son, James, serving alongside his dad, hoisting sails and, perhaps most importantly, taking pictures of the guests at their request. “The Endeavor is such a great equalizer,” Sue continues. “It doesn’t matter who you are. If you’re a senator or a school teacher from Kansas, you all have the same experience.”

By definition, the word endeavor means to work hard to achieve something over a long period of time. The name was fitting for a boat built in a backyard from pieces scrapped from a Fall River lumberyard. Yet as Jim’s thirty-foot sloop sails into its fifth decade, the Endeavor has truly fulfilled its destiny. “People see us as part of their Nantucket experience every year,” Sue says. “They go to the Juice Bar, they go to Cisco, and they sail on the Endeavor.” As we chat, a group fills in, taking seats on the wooden bench in front of their slip, waiting to board for their sail. James is here, alongside his father, and as they get ready to welcome the passengers aboard, Sue says with certainty, “This is the essence of Nantucket. This is it.”