MIDDLE ISLAND - A 14-year-old boy died yesterday following a Jet Ski accident on the Peconic Bay off of the North Fork. Dominic Trionfo, of Middle Island, was riding a Jet Ski near Mattituck yesterday at around 2 p.m. when the accident happened. Police tell News 12 Long Island that Trionfo collided with the anchor chain of his family's boat. The teen was treated at the scene and then rushed to Peconic Bay Medical Center, where he died.Relatives say Trifono was on his very first solo Jet Ski ride after getting his license. Ten family members witnessed the tragic accident.Trionfo was a freshman at Longwood High School and played on the football team.