There's a new attraction for thousands of people enjoying the long holiday weekend on North Carolina's Outer Banks.

Shelly Island is a destination you won't find on a standard map. The giant barrier island suddenly formed in the Atlantic Ocean, almost overnight.

CBS News correspondent Mark Strassmann reports the mile-long island, which measures as wide as a football field, has attracted hundreds of tourists by boat for the Fourth of July.

Pilot Larry Ihler told Strassmann the island "has definitely gotten bigger" and is "more built up."

Strassmann set out by kayak on Monday to explore Shelly Island with County Commissioner Danny Couch, who is a life-long resident of the Outer Banks.

Couch says he's seen barrier islands pop up before, but not like this one, which he first noticed in April.

"This is the mother of all sandbars," Couch said. "All of a sudden, right here where we're sitting. It's a hoss. It's huge. It is big."

The area off North Carolina's coast is one of the most dynamic ocean environments on Earth -- nicknamed the "graveyard of the Atlantic" -- with more than 2,000 documented shipwrecks since 1585.

This mile-long sandbar, dubbed "Shelly Island" for its plethora of seashells and colorful pebbles, has been forming and growing since late spring.

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Two powerful currents collided there -- the Gulf Stream from the Caribbean flowing quickly north, and the Labrador Current from the arctic pushing south.

The currents collide, churning surf and sand at Diamond Shoals, creating a cluster of shifting underwater sandbars off the coast of Cape Hatteras. Satellite imagery shows the large shoal has continued to grow ever since it surfaced last March.

"Nobody will ever be able to predict what's going to come out of the ocean or what it's going to look like," Couch said.

Over Memorial Day, 11-year-old Caleb Regan visited the island for the first time. He noticed shells scattered everywhere and gave the place a name that stuck: Shelly Island.

"I thought it would just be like a little family nickname," Caleb said. "I can't believe it got this big. Very incredible."

Strassmann says tourists keep coming to Shelly Island, both for the shells and the novelty. But aside from its beauty, the island presents potential trouble -- sharks swimming near boaters and waders. It's so new that no federal or state agency regularly patrols the area.

"Right now, nobody's really claiming ownership," Couch said. "It's sort of a no man's land. This could be yours, or mine, or somebody's. But it belongs to the American people. It's a phenomenon. Enjoy it while we have it."

Before you rush here to build a beach house, remember that nature gives and nature takes away. The first hurricane that comes along could blow the island, as big as it is, back into the Atlantic.

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Shelly Island: The new beach off North Carolina's Outer Banks - CBS News