A teenager is being charged as an adult after he allegedly waved a gun on a Florida beach filled with spring breakers and then stood off with deputies who chased him into the Atlantic.The incident in New Smyrna Beach, a city on Central Florida’s Atlantic coast, happened Thursday afternoon when deputies patrolling the beach, populated with festive spring breakers, came across a fistfight, body camera footage showed.A crowd formed, and from it appeared to emerge a person waving a gun, the footage released by the Volusia Sheriff’s Office showed. “He’s got a gun,” people in the crowd…