Story highlights "We don't know what secrets are going to be held on the ship," says explorer

Barry Clifford says the wreck is in the right place and is the right size

A cannon of 15th century design found at the site is the "smoking gun," he says

Evidence is "very compelling," says an archaeological expert

Is a sunken shipwreck off Haiti the long-lost remains of the Santa Maria, Christopher Columbus' flagship from his first voyage to the Americas?

Underwater explorer Barry Clifford, who led a team that found and investigated the wreck, says he's confident it is.

"Every single piece fits. Now, of course, we have to go through the whole archeological process, and we plan to do that within the next few months, but I feel very confident that we've discovered the site," he told CNN.

"This is the ship that changed the course of human history," Clifford said.

Photos: History's biggest mysteries Photos: History's biggest mysteries Stories of elusive giant hairy, human-like beasts have been told on several continents for centuries. In the Himalayan Mountains, it is known as the Yeti or the Abominable Snowman. North Americans have reported sightings of Big Foot or Sasquatch. Russians call theirs the Almasty. Hide Caption 1 of 12 Photos: History's biggest mysteries The location of the Santa Maria, Christopher Columbus' flagship for his journey to the new world, has remained a mystery since it ran aground in late 1492. Underwater explorer Barry Clifford believes these are the remains of Columbus' Santa Maria off the coast of Haiti. Hide Caption 2 of 12 Photos: History's biggest mysteries The earliest documented sighting of a mysterious creature swimming in Scotland's Loch Ness came in 1871, according to the monster's official website . Dozens of sightings have been logged since then, including the most recent in November 2011 when someone reported seeing a "slow-moving hump" emerge from the murky depths of Loch Ness. Hide Caption 3 of 12 Photos: History's biggest mysteries The twin-masted merchant vessel Mary Celeste set sail from New York on November 7, 1872, bound for Genoa, Italy. Its 10 passengers were not on board when it was found floating in the Strait of Gibraltar four weeks later. There were no signs of a struggle, and all of the boat's cargo was still on board. Its only lifeboat was missing. Hide Caption 4 of 12 Photos: History's biggest mysteries The name Jack the Ripper came from a letter sent in 1888 to London police, purporting to be the killer of five prostitutes. His true identity has never been proved. Hide Caption 5 of 12 Photos: History's biggest mysteries The Shroud of Turin may be the most famous religious relic.

Some Christians believe the shroud, which appears to bear the imprint of a man's body, to be Jesus Christ's burial cloth. The body appears to have wounds that match those the Bible describes as having been suffered by Jesus on the cross. Many scholars contest the shroud's authenticity, saying it dates to the Middle Ages, when many purported biblical relics -- such as splinters from Jesus' cross -- surfaced across Europe. Hide Caption 6 of 12 Photos: History's biggest mysteries The Lockheed Electra piloted by Amelia Earhart and Fred Noonan flies over the Golden Gate Bridge at the start of a round-the-world flight on March 17, 1937. The two vanished during a similar flight in 1937. Hide Caption 7 of 12 Photos: History's biggest mysteries A group of U.S. Navy Avenger planes, like the ones seen here in 1943, disappeared off the coast of southern Florida in December 1945. The planes were carrying 14 men. Thirteen more servicemen also vanished when they went to search for the missing fliers. That started the legend of the Bermuda Triangle. Other mysterious disappearances over the years have been linked to the Triangle, which is anchored by Bermuda, Florida and Puerto Rico. Hide Caption 8 of 12 Photos: History's biggest mysteries The Los Angeles County coroner ruled that actress Marilyn Monroe's death in this room was a "probable suicide" from an overdose of barbiturates. Despite the official conclusion, questions have lingered for decades about Monroe's death in August 1962 at the age of 36. Hide Caption 9 of 12 Photos: History's biggest mysteries U.S. President John F. Kennedy sits with the first lady in the back of a limousine November 22, 1963, in Dallas. Kennedy's assassination remains one of the most shocking events of the 20th century, and it's one of its biggest mysteries. While a blue-ribbon panel concluded that there was only one gunman, a Gallup survey six decades later found that 60% of Americans don't believe that. Hide Caption 10 of 12 Photos: History's biggest mysteries Police sweep a field in Waterford Township, Michigan, in search of Jimmy Hoffa's body in July 1975. The ex-Teamsters boss was last seen that month outside a Detroit-area restaurant. His disappearance is a mystery that triggers occasional digs by FBI agents looking for his remains. Hide Caption 11 of 12 Photos: History's biggest mysteries Actors Robert Wagner and Natalie Wood are seen on their boat the Splendour in October 1976. Wood's body was found floating off California's Catalina Island in November 1981. It was initially ruled an "accidental drowning," but the Los Angeles County coroner officially changed the death certificate last year to read "drowning and other undetermined factors." Hide Caption 12 of 12

If the claim is confirmed, it would go down as one of the most significant underwater archaeological discoveries ever.

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"It is the Mount Everest of shipwrecks for me," said Clifford, 68.

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But it isn't a new find for him. Clifford's announcement involves a wreck he and his team investigated in 2003. A cannon was found as part of the wreck. But, Clifford told CNN, archaeologists at the time "misdiagnosed" the cannon.

Two years ago, after having researched the type of cannon used in Columbus' time, "I woke up in the middle of the night and said, 'Oh my God,' " Clifford told CNN. He realized the 2003 find might have been the one.

A couple of weeks ago, he returned to the wreck with a group of experts. The team measured and photographed the ship. But some items, including the cannon, had been looted from the ship in the intervening years, Clifford said.

The ship "still has attributes that warrant an excavation to determine the site's identity," archaeologist Charles Beeker of Indiana University said Tuesday. "Barry may have finally discovered the 1492 Santa Maria."

The evidence, Beeker said, is "very compelling."

The ship was found in the exact area where Columbus said the Santa Maria ran aground more than 500 years ago, Clifford said. The wreck is stuck on a reef off Haiti's northern coast, 10 to 15 feet beneath the water's surface.

Clifford plans to go back to Haiti next month to meet with authorities and decide what steps to take next.

Wrecked in 1492

It was the flagship of Columbus' small fleet that set sail from Spain in August 1492 under the sponsorship of King Ferdinand II and Queen Isabella I.

The voyage aimed to find a westward route to China, India and the gold and spice islands of the East. But the land the sailors set eyes on in October 1492 was an island in the Caribbean.

Among the islands on which Columbus set foot was Hispaniola, which is divided between Haiti and the Dominican Republic. Columbus established a fort in Haiti.

That December, the Santa Maria accidentally ran aground off the island's coast. Some planks and provisions from the wrecked ship, which was about 117 feet (36 meters) long, were used by the garrison at the fort, according to Encyclopaedia Britannica.

Columbus set off back to Spain with the two remaining ships, the Nina and the Pinta, in January 1493.

Archaeological study needed

Archaeologists will have to excavate and examine the ship found off Haiti in order to determine whether it is, in fact, the Santa Maria.

Most of the ship is in shape and will be possible to excavate with the help of the Haitian government, said Clifford, who made a name for himself salvaging pirate ships off the coasts of Cape Cod and Madagascar.

His team has used sophisticated metal detectors and sonar scans to study the remains.

The ship is the right size, he said, and stones found at the site match the kind from the part of Spain where the ship was built.

"I don't think any of us should take for granted what has been written," Clifford said. "This is a tremendous touchstone to that period in time. We don't know what secrets are going to be held on the ship."