The great white shark was just enjoying a snack -- which in his case was the carcass of a whale -- when four Long Island fishermen spotted him. And now the big fish is all over YouTube.

"He's huge, that's the biggest shark I've ever seen up close," said Michael Maiale, 33, of Island Park, one of the four who encountered the elusive and enormous fish. "We probably saw at least 50 different sharks, but only the one great white," he said.

Maiale and his friends were looking to catch sharks around an offshore wreck last Sunday when they saw an unusual object about 45 miles off Jones Beach.

VideoShark diving off the East End

At first, it appeared to be a boat. Drawing closer, they realized it was about as perfect a meal a shark could ever hope to find, a dead whale perhaps 40 or so feet long.

Many sharks had discovered it, but the great white did not put in an appearance for about a quarter of an hour.

Then "I saw in my depth finder a really big mark, and I said 'There's got to be something really big here,'" Maiale said.

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"He just went right under the boat,'" said Maiale, a New York City emergency medical technician.

"When it would come up to the back of the boat, I could have honestly touched it with the back of my hand without really reaching," said Liam Lyons, 22, of Smithtown, a pre-med student at St John's University.

Equipped with one of his Go Pro cameras, Lyons began shooting six hours of video, which he and Maiale condensed into a three-minute video.

Maiale, who thought his friends might like to see it, posted it to his Facebook. When he went to bed that night, there were 25 to 50 views.

"The next morning, I had like 25,000 views, and then it just kind of took off from there, now there are over 550,000 views," he said.

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"Most of the underwater stuff, it was four to six feet" away, said Lyons, who attached his camera to a pole to obtain that footage.

John Chisholm, a biologist with the Massachusetts Division of Marine Fisheries Shark Research Program, confirmed the shark in the video was indeed a white, another name for a great white.

"It's a male white shark," Chisholm said, explaining that when it rolls upside down to feed on the whale, it reveals "claspers," two appendages located on the bottom fin.

Maiale named the great white Rudy, in honor of his late grandfather.

Maiale's boat, "The Angry Tuna," is about 29 feet long, which helped Chisholm judge that Rudy is only about 11 or 12 feet long, and thus is a teenager who has yet to become sexually mature.

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"White sharks can get to over 18 feet; we estimate their maximum size to be about 20 or 22 feet, they grow very slowly," said Chisholm.

He saluted Maiale and Lyons as citizen scientists whose video enables him to begin tracking Rudy, thanks to his unique markings, for his research.

"You'll see the little white spot on the tail, and the markings on the gills, those markings are like fingerprints," Chisholm said.

"It also has a little nick on one of its fins, on the right side," he said.

Great whites are a prohibited species in the United States so they cannot be caught or killed.

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With any luck, Rudy will live as long as many humans. "Some of the bigger sharks can actually live over 50 years, and a recent report suggests they can even live to 70 years," Chisholm said.

The young great white exhibited typical shark curiosity when he encountered the fishermen's boat. "He just kind of swam around the boat, checked us out," said Lyons.

Then his attention returned to the whale, though Rudy was more of a grazer than a sit-down and linger type. When he disappeared occasionally, smaller sharks would return.

Maiale and his friends caught a couple of blue sharks they released during one of Rudy's absences. The great white found this intriguing.

"At one point, we were reeling in one of the blue sharks, when the great white charged at it," Maiale said. "Luckily, we got him up to the boat and cut him loose."

Lyons said: "That's when he got really interested in the boat, he got really close."

No one knows how many great whites live in the Atlantic, said Chisholm, who hopes his research answers this question, as well as many others, including their migratory patterns.

He urged fishermen or boaters to send him any pictures or videos of shark sightings they might have to: john.chisholm@state.ma.us

For the four fishermen, it was an encounter they will never forget.

"It was a real adrenalin rush experience," Lyons said, "We were like 'Oh my God, this is something unbelievable.'"