On November 10, 2007, about 1915 Pacific standard time, a Piper PA-34-200T, N3038P, overran the runway at Napa County Airport, Napa, California. Atkin Air, LLC, was operating the airplane under the provisions of 14 CFR Part 91. The commercial pilot was not injured, and the airplane sustained substantial damage. The repositioning flight departed Napa about 1915, with a planned destination of Lincoln Regional Airport - Karl Harder Field, Lincoln, California. Instrument meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan had been filed. In a written report to the National Transportation Safety Board, the pilot stated he unloaded the passengers at the FBO and was returning to Lincoln. He noted he had been distracted, and neglected to latch the front cargo door. During takeoff, the cargo door opened and the pilot decided to abort the takeoff. He opined that the wet runway caused the airplane to hydroplane, which made stopping difficult. The airplane overran the runway, continued about 200 yards, collided with a fence, and came to rest in a water-filled canal. The pilot reported no preimpact mechanical malfunctions or failures with the airframe or engine.