MOORHEAD - As many as 200 students decided to celebrate graduation at Concordia College by skinny dipping in a murky campus pond early today, authorities said. A security officer tried to shoo the students out of the pond but they wouldn't cooperate, Concordia security chief Sherri Arnold said. Moorhead police were called after students pushed the security officer's golf cart into the pond. Although no one was arrested, several people could face charges. Arnold said 10 people were identified because they left their clothes and wallets behind. Sunday was graduation day at Concordia.