A Mattituck man was arrested on Aug. 8 after a boating accident in Sag Harbor Bay.According to Sag Harbor Village police, Brandon J. Sill, 34, was at the helm of the Burley Hillbilly when, at about 10 p.m., the 39-foot craft struck a rock and took on water. Mr. Sill could not say exactly where it happened, said Robert Bori, the village harbormaster. Police removed him from the boat and took him to the nearest land, Fahys Road on North Haven, where field sobriety tests were administered. He was determined to be intoxicated At the time of the accident, there was an 8-year-old aboard the boat. Mr. Sill was charged with operating a vessel in an intoxicated condition and endangering the welfare of a child, both misdemeanors. Held overnight for arraignment in Sag Harbor Village Justice Court, he was released later that morning on $250 bail.