The 36-foot luxury motorboat, with its polished mahogany hull and American flag waving from the stern, set off from East Hampton on a recent Sunday morning, heading toward the tip of downtown Manhattan and passing beneath airplanes, bridges, thunderstorms and, eventually, a glorious blue sky. The trip would take the boat, named Belle, within view of the Statue of Liberty en route to the Hudson River and, finally, Lake Erie.

But first, she needed to navigate a narrow stretch of water that has haunted sailors for centuries: Hell Gate, a tidal strait named by Dutch explorers in the 1600s, where the currents of the East River, Harlem River and the Long Island Sound converge.

In just a few harrowing moments, Belle churned through the rough waters, and her crew exhaled.

“That was definitely hair-raising,” said the captain, Geraldo Rivera, his own tresses (and mustache) looking wind-tousled.

This was Day 1 of an eight-day voyage that Mr. Rivera and his brother Craig Rivera had embarked on to bring Geraldo’s boat from Hampton Bays, where he had spent an extended vacation with his wife and youngest daughter, to the suburbs of Cleveland, where they live.

Mr. Rivera, who turned 80 on the Fourth of July, had found himself out of work for nearly the first time since the early 1970s when he emerged onto the journalism scene as a swashbuckling muckraker. In June, after 22 years at Fox News, he was demoted by the network (“humiliated” is how he put it), and so he quit.

Mr. Rivera had enjoyed political relevance late into his career, thanks in part to a longstanding friendship with Donald Trump, dating back to the 1970s. That relationship ended in November 2020, he said, after he refused to endorse Mr. Trump’s contention that the election had been stolen from him. It was, he said, “the beginning of the end” for him at Fox.

His sudden unemployment, and perhaps the comfort of life on the water, left him unconstrained to talk openly about the ordeal that began with his dramatic falling out with the former president.

As Mr. Rivera considered what his future might be, he wanted and maybe even needed an adventure. In his earlier decades, he would have set sail on the open sea. But with a cane in his hand and a daughter about to enter her senior year of high school, that did not seem feasible. Instead, he set his sights inland.

Mr. Rivera loves rivers. And — it turns out — canals. Huge fan of canals.

This trip would take the Rivera brothers up the Hudson River into the Erie Canal and through 36 locks — water elevators that would help them climb nearly 600 feet from the surface of the Hudson to the more elevated Lake Erie.

To his mind, the Erie Canal, which opened in 1825 and connects the Great Lakes to the Hudson River, is the king of them all. “The most important public works project ever,” Mr. Rivera said. “The Erie Canal made New York the city at the center of the world.”

New York’s past was not the only history on his mind. His own weighed heavily in the air. The big birthday, along with the unexpected change in his career, left Mr. Rivera nostalgic as he steered his ship home. “It is a passage,” he said, “in every way.”

Baywatch Guest Star

Mr. Rivera is a selfie magnet.

The prolific hair, prodigious mustache, broadcast-perfect voice: He has been one of the most recognizable TV journalists for generations and is constantly approached for photos. Spend even a little time with him, and the appeal of floating peacefully in the middle of a canal becomes obvious.

At a marina in Mt. Sinai, N.Y., on Long Island Sound, the Rivera brothers stopped after white-knuckling through an early morning thunderstorm, to fuel up with sausage-and-egg sandwiches and gas. As they were readying to board Belle and head toward New York City, a woman approached. “Can I get a picture?” she asked. A moment later, Geraldo was surrounded by a group of 10. He leaned on his cane and smiled gamely before heading back out to sea.

Geraldo sat at the helm of Belle, a Picnic Boat built in 1998 by Hinckley Yachts of Maine. He purchased it from the original owner in 2000 for $500,000.

The steering wheel and navigation screen were in front of him, a gear stick that controls speed and direction to his right. Over the back of his captain’s chair was a red lifeguard’s windbreaker with his name embroidered on it. The jacket was a gift from the actor David Hasselhoff after Mr. Rivera guest-starred on an episode of “Baywatch” in 1994.

Craig was the mate, the crew, the mechanic, the fixer to his brother’s frontman. The few times he took the wheel himself, his big brother shouted orders to him from the back of the boat.

For decades, Craig, 68, was a producer and cameraman working for Geraldo, a gig that included 10 trips to Afghanistan — bringing hidden cameras to meet with opium dealers and Taliban strongmen.

The heart of this adventure would take place once the brothers motored past the city and into the belly of the Hudson — the Catskill Mountains, West Point, Albany — and on to the locks and small towns of the canal and beyond.

But on this first day, traveling the waters near New York City, Geraldo was revisiting the channels of his life.

A Son of (West) Babylon

He passed Babylon, N.Y., near West Babylon, where he was raised with four siblings by a Puerto Rican father and Jewish mother. (Reflecting his parents’ midcentury American dreams of assimilating, he was then known as Gerry Riviera.)

He zoomed past the State University of New York Maritime College, which he attended for two years after high school, with plans of becoming a merchant marine or joining the U.S. Navy, before he transferred to the University of Arizona, where he played lacrosse.

He captained Belle under the Williamsburg Bridge, near Brooklyn Law School (class of 1969) and veered right before reaching the Verrazano Bridge that connects Brooklyn and Staten Island, which is where Mr. Rivera made his journalistic name in 1972 by exposing the abuse of children institutionalized at Willowbrook State School.

As he tooled up the river, between New Jersey and the West Side of Manhattan, he pointed toward various neighborhoods and buildings where for decades he worked.

He was a correspondent for ABC News’s “20/20” and then hosted a special in which tens of millions of viewers watched him open a vault belonging to Al Capone. (The vault was empty, but the debacle made him famous.)

He hosted and produced an eponymous syndicated daytime talk show, for 11 years. He likened it to having “a money tree in my backyard,” as it helped create the “trash TV” canon (in 1988, he got his nose broken on the air when white supremacists and Black activists started throwing punches and chairs).

He joined CNBC, hired in 1994 by Roger Ailes, to start a nighttime talk show, “Rivera Live,” where he went all-OJ-all-the-time and where he embarked on what he called “an office affair” with one of his producers, Erica Levy — 32 years his junior and now 20 years his (fifth) wife. (He has one child with Ms. Rivera and five in total.)

He followed Mr. Ailes to Fox News in 2001, becoming a war correspondent and then a talking-head, providing what he calls “a progressive, independent” voice. A registered Republican, Mr. Rivera’s commentary was reliably pro-cop, pro-choice and, until late 2020, pro-Trump.

As Mr. Rivera steered his boat around the islands that were once his home toward his new home in the Midwest, where he, his wife and their teenage daughter live near Ms. Rivera’s family, he kept his gaze on the water, mostly undistracted but for the sporadic text he dictated to his wife (“Love you, baby”) and an occasional phone call. “I suppose,” he explained to a buddy, “this is sort of ‘Geraldo’s last journey into exile in Cleveland.’”

‘That may sound small.’

Early on Day 2, after waking from the below-deck sleeping chamber they shared, the Rivera brothers sipped their Taster’s Choice instant coffee from tumblers imprinted “Belle.” They shoved off from Newburgh, N.Y., at 7:20 a.m., with many miles to cover.

Today’s stretch, a mostly rural landscape with verdant vistas, would be more suitable for talking: About Mr. Rivera’s career at Fox News. About Mr. Trump. About the ways they were entangled.

As two men building their careers in New York in the 1970s, ’80s and beyond, Mr. Trump and Mr. Rivera became good friends. They went to the fights in Atlantic City together and to the clubs of Manhattan.

In 2015, they went on TV together too, with Mr. Rivera competing on Mr. Trump’s “Celebrity Apprentice.” Weeks into the season, contestants including Lorenzo Lamas, formerly of “Falcon Crest,” and the pop idol Kevin Jonas had been weeded out, leaving Mr. Trump to choose a winner between Leeza Gibbons, the former co-host of “Entertainment Tonight,” and Mr. Rivera.

This was a turning point in their friendship, Mr. Rivera said. When Mr. Trump announced on the show that Mr. Rivera had lost to Ms. Gibbons, he never bellowed his famous “You’re fired!” at Mr. Rivera. This engendered Mr. Rivera’s loyalty to Mr. Trump for years to come. “I realize that may sound small, but it meant a lot to me.”

The 2016 election gave Mr. Rivera — well into his 70s and past the point where many of his contemporaries had retired — renewed relevance. He suddenly found himself in a situation where “my old friend is the president, and he is giving me tremendous access.” When President Trump visited Puerto Rico in the aftermath of Hurricane Maria, Mr. Rivera appeared there with him.

All through the Trump administration, Mr. Rivera remained a fierce defender of the president and his policies — on Fox and on Twitter. But the relationship took a quick turn 10 days after the 2020 election, Mr. Rivera said, when Mr. Trump called him and asked if he had ever heard of Dominion Voting Systems, a company that Mr. Trump said had helped turn the results in Joe Biden’s favor. Mr. Rivera said he had not heard of it. Mr. Trump asked him to look into the allegation and to call him back.

Mr. Rivera said he contacted sources who assured him that Dominion was not involved in election interference. He said he called the White House on Nov. 16 to share his findings with Mr. Trump. The president did not take the call, he said, and they have not spoken since. Mr. Trump did not respond to a request for comment.

Fox and Former Friends

Mr. Rivera began to assert publicly that Mr. Biden had lawfully won the election and that Mr. Trump — who is currently facing 91 felony counts, including many connected to election interference — should acknowledge his loss. On Jan. 7, 2021, Mr. Rivera posted a video on Twitter calling the attack on the U.S. Capitol a “physical assault on our democracy” that “was the product of Donald Trump’s selfish, inflammatory rhetoric.”

In the months and years ahead, Mr. Rivera denounced theories of election fraud espoused by colleagues at Fox, and argued for the second impeachment of Mr. Trump. Mr. Rivera said that he continued to make appearances on “The Five,” the network’s popular current-events talk show, but said he was booked with less frequency on that and other shows.

He also tangled with other Fox personalities in public.

In October 2021, Mr. Rivera made headlines after using a crude term in a tweet to dismiss one of Tucker Carlson’s conspiracy theories about Jan. 6. Mr. Rivera said he was scolded afterward, and a few of his planned on-air appearances disappeared from the schedule. “I was sent to the bench,” he said. (This spring, Mr. Carlson was pushed out by Fox News less than a week after the network agreed to settle Dominion’s defamation lawsuit for $787 million.) Mr. Carlson did not respond to a request for comment.

Last year, in an on-air argument about abortion with Greg Gutfeld, one of the co-hosts of “The Five,” Mr. Rivera called his colleague “an insulting punk.” Mr. Rivera said that during a commercial break, he called Mr. Gutfeld “thin-skinned and a crybaby.” (A spokeswoman for Mr. Gutfeld said that Mr. Rivera subsequently apologized for his reaction. Mr. Rivera denies this.)

More of Mr. Rivera’s planned appearances on “The Five” disappeared from the schedule, he said: “I was read the riot act.”

In June, executives notified Mr. Rivera that he would no longer appear on “The Five” but could make documentaries for the network. Mr. Rivera felt he was being pushed into obsolescence and quit.

Less than two months later, in the quiet of his river trip, Mr. Rivera continued to grapple with conflicting feelings. He called Mr. Trump “crazy, really crazy,” and also “underrated, over-prosecuted and persecuted.”

“I feel awful that he made me dump him,” Mr. Rivera said.

Asked to speak in more detail about Fox, he demurred. “I cashed their checks for 22 years,” he said. When asked to comment, a Fox spokeswoman said that when Mr. Rivera made his final on-air appearance on June 30, he said, “I love Fox, I love the people at Fox.”

As they approached the Erie Canal, Mr. Rivera had more immediate concerns: Belle was making an ominous noise. The brothers had made it through just one lock, with 35 and more than 500 miles to go.

To address the problem, Craig would need a grease gun, a tool that helps lubricate the drive shaft. He dialed a contact at the New York State Canal Corp., which manages the waterway. The canal guy located a grease gun, but Belle would need to make it to Lock E-7 for them to collect it.

For the next several hours, Geraldo motored the boat, slowly, into one lock after another. Each time, he cut the engine, and the steel gates at the back of the lock snapped shut. The water, and the boat upon it, began to rise.

In Lock E-6, the tension was palpable, even with Bruce Springsteen’s “Erie Canal” playing in the background from Mr. Rivera’s phone.

“I want you to kill the engine and grab this rope,” Craig said.

“I’ll kill the engine, but I hope it starts again,” Geraldo said. Luckily it did.

At Lock E-7 in Niskayuna, N.Y., they met up with two men from the Canal Corp. The men handed over the grease gun, and within minutes Belle was purring quietly again.

Craig popped open two Corona Lights. They clinked bottles. “I am so happy to have my boat back,” Geraldo said as he headed to Schenectady. “Oh, what a relief.”

It would be six more days before the brothers made it to Cleveland. There would be a busted bow-thruster, a broken fan belt, intense westerly winds, banging waves that caused them to strap into life vests, an unexpectedly rowdy party scene in Erie, Pa., and photos, so many photos, taken with people they met along the way.

“It was exactly what a prolonged sea journey should be — everything from boredom to absolute terror,” he said.

Mr. Rivera is now back in Cleveland, relieved to be home, and “giving myself until Labor Day to decide what’s next, if anything at all.”

“I’m onto a new journey,” Mr. Rivera said. “The rest of my life.”

Audio produced by Tally Abecassis.