Fishermen push their boat into the sea in the fishing town of Ahuchapan, the hometown of castaway fisherman Jose Salvador Alvarenga, February 4, 2014. Jose Salvador Alvarenga, 37, told officials he set sail on a shark fishing trip from Mexico in late December 2012 - some 10,000 km (6,200 miles) away - but was blown out to sea. He survived more than a year adrift in the Pacific Ocean, drinking turtle blood and catching fish and birds with his bare hands. Reuters

“It was only about a half hour after I came ashore on Marie-Galante near Guadeloupe that my parents found out I was alive,” Steven Callahan recalled, describing the day in 1982 when he first touched land again after spending 76 days adrift in a rubber life raft.

“Word spread amazingly fast, and within days I was fielding phone calls from all over the world. Publications wanted me to sell them exclusives, and that sort of thing went on until I arrived back home in the United States and had a run-in with the guy in the Coast Guard in charge of my case. Suddenly -- based on a miscommunication and some almost truths, the stories about me in the press changed: I was a hoax.”

Callahan, whose 1986 memoir “Adrift: 76 Days Lost At Sea” was on the New York Times bestseller list for more than 36 weeks, said he’s seen this sort of reaction to castaway tales time and again. “We’re momentary heroes and then people say, ‘Wait a minute. What’s going on here? Did this really happen?’ While it’s hard to prove a hoax, the real explanation is often even more ridiculous.”

It took Callahan some time to prove that he was not a young man out to sink the only thing he owned (his ship), cover his skin in saltwater sores and lose a third of his body mass in exchange for 15 minutes of fame and a book deal. So when he hears about men like José Salvador Alvarenga, who washed up in the Marshall Islands last Thursday alleging a staggering 14 months at sea, he can’t help but give them the benefit of the doubt.

Alvarenga’s tale has boggled the minds of just about everybody who’s heard it -- and it begins in the most unlikely of places: the small Mexican fishing hamlet of Costa Azul. A humble and rotund man, Alvarenga was known to his fellow shark fishermen as “La Chancha” (or the pig), but was otherwise “missing” to friends and family in his native El Salvador for nearly a decade before he truly disappeared into the Pacific some time in late 2012.

By all accounts, no one had heard from the man for more than a year before he miraculously washed up on the remote coral atoll of Ebon last Thursday, some 6,600 miles (10,800 kilometers) away. Speculation over the veracity of his story was rampant the moment photos surfaced of Alvarenga waving a Coke can in the capital of Majuro on Monday: Could this bushy-haired man who looks neither emaciated nor particularly sunburnt have survived at sea longer than anyone else in recorded history?

Though verified information is scant, what we know so far is that shocked islanders claim to have discovered the 37-year-old in tattered underwear last Friday morning. A Norwegian anthropology student working on Ebon Atoll described seeing the fisherman’s 24-foot fiberglass boat on a beach covered in barnacles and littered with turtle carcasses, fish remains and a baby bird, but no fishing gear.

Alvarenga later told reporters that he survived his ordeal by eating turtles, seabirds and fish, and drinking the animals’ blood or his own urine when rainwater was scarce. The castaway added that this diet proved too gut-wrenching for a companion, identified as 24-year-old Ezequiel Córdoba Barradas, who died about four months into the journey and was tossed overboard.

Mexican authorities have confirmed that Alvarenga lived for more than a decade in the state of Chiapas, where Costa Azul is located, while the Chiapas state civil protection agency noted that it had deployed aircraft and boats in search of two men in November 2012 -- though there are some slight discrepancies in the names.

Despite these time stamps, critics say several aspects of the story don’t add up. Alvarenga simply looked too good in those first photos to have been alone in a rocking boat for more than a year, they say. Those chubby cheeks and that white skin, they add, were not the look of a man who had spent 14 months baking under the unrelenting tropical sun with neither fishing gear nor a morsel of conventional food to eat.

"It does sound like an incredible story and I'm not sure if I believe his story," Gee Bing, acting secretary of foreign affairs for the Marshall Islands, told Associated Press early on, fueling the debate. "When we saw him, he was not really thin compared to other survivors in the past. I may have some doubts.”

As the story evolved, others questioned the similarities between Alvarenga’s case and that of three Mexican shark fishermen who were discovered by a Taiwanese fishing trawler off the coast of the Marshall Islands in August 2006. Lucio Rendón, Salvador Ordóñez and Jesús Eduardo Vidaña said they survived nine months at sea on fish, turtles and gulls and, like Alvarenga, turned to God for the will to survive after two of their companions died.

The 2006 case is startlingly familiar not only in how it reportedly happened, but in how the media reacted after the fact. The three fishermen faced widespread doubts over the validity of their story, while the sensational coverage was at best riddled with stereotypes and at worst puffed up to paint the men as drug lords, cannibals and killers -- all of which they vehemently denied (and all of which are slowly creeping into the coverage of Alvarenga’s story).

Given the scattered and, at times, unbelievable evidence of four men who claim to have crossed the Pacific Ocean from Mexico to the Marshall Islands in the past decade, what can we conclude? Are they all lying? Is Alvarenga’s exceedingly long survival story that of a castaway copycat? And if he’s a copycat, where did he spend the past 14 months?

Perhaps some of the answers lie in science.

Big Current, Small Boat, Tiny Ecosystem

Dr. Erik van Sebille is a physical oceanographer at the University of New South Wales who studies currents in the Pacific Ocean. From an oceanographic point of view, he believes Alvarenga’s story is certainly possible. “If you look at the currents of the tropical Pacific, they could bring you from Mexico to the Marshall Islands in between one and two years,” he explained.

Van Sebille said that the reason for such a broad window is that the ocean is not at all like a simple river. “It’s actually quite chaotic and full of eddies or vortexes that whirl around. So it would really depend on several factors like whether you have tailwind or backwind and what season you start the journey.”

The oceanographer’s primary interest lies in tracking how rubbish ends up in the Great Pacific Garbage Patch. He said that if the average rate for a plastic bag to travel from the Mexican Coast to the Marshall Islands was about 1.5 years, a boat could do it in about 13 to 14 months, “which lines up perfectly in the current case.”

But even if a boat could make it from one end of the Pacific to another in roughly the same amount of time in question, that still doesn’t clarify how one could survive on that boat for upwards of 14 months.

For those answers, we turn to Nick Vroomans, director of the Queensland, Australia-based Staying Alive Survival Services, which teaches classes in sea survival. He explained that the equatorial Pacific is actually very plentiful. “Let’s use the analogy on land of surviving in the dessert versus surviving in an equatorial jungle. Some places are naturally more conducive for people to live and the sea is the same. There are places where it would certainly be hard to survive, but the area of the Pacific we’re talking about is quite abundant with rain, sea turtles and seabirds.”

Vroomans said Alvarenga’s boat could have acted like its own tiny ecosystem. “In these warm waters, smaller fish would likely congregate under the boat and attract bigger fish. Then the seabirds would come and use the boat as a landing pad in the open ocean and feed off the fish. So the boat creates its own environment, and there is every chance that one can catch food.”

Vroomans’s gut feeling about the case is that it’s certainly plausible if Alvarenga had some sort of protection from the elements like a tarp or sail and a way to collect rainwater -- “though there are threads to the story that need to be figured out.” He noted that others had endured similar voyages both in recent history and in the time of Pacific Island exploration.

Indeed, the once-crackpot theory that Pacific Islanders and Native Americans had contact in Pre-Columbian times gained weight in recent years following several archeological finds in Chile and Southern California.

Conventional wisdom says humans arrived in the Americas thousands of years ago crossing an ice bridge from Siberia to Alaska. Based on some distinctive eighth-century Polynesian canoe technology found in California and a pile of 14th-century chicken bones found in Chile -- not to mention the perplexing linguistic and cultural ties between Polynesians and Chile’s indigenous Mapuche people -- Polynesian explorers may have “discovered” the Americas and its inhabitants long before Leif Ericson or Christopher Columbus.

Evidence of American sweet potatoes planted in the faraway Cook Islands around 1000 A.D. further suggest that explorers may have visited South America and drifted back across the Pacific to Polynesia on small boats with very little technology, much like our modern-day castaways.

So could Alvarenga’s unbelievable journey harken back to one of Earth’s most magnificent migration routes? Moreover, is his miraculous survival -- 259 days longer than the previous record holder, Poon Lim, who drifted from South Africa to the mouth of the Amazon in 1942 -- really so unheard of?

“When you think about it, we have no idea how many people have been out there even longer and have never come back,” Stevens said. “And I think these situations happen a lot more than we know about.”

We may never be able to prove that “La Chancha” survived in that fiberglass fishing boat for as long as he says he did without ever setting foot on some speck of land in the middle of the vast Pacific Ocean. It may be completely improbable, but it’s starting to look like there is every reason to believe it’s within the realm of possibility.