RIVERINE DRILLS U.S. Navy Petty Officer 3rd Class Geoffrey Martin, assigned to Riverine Squadron 1, fires a GAU-17A gun from the bow of a riverine assault boat during live-fire battle drills on Fort Knox, Ky., March 28, 2010. SHARE: Download: Full Size (0.08 MB) Credit: VIRIN: 691201-P-IFC78-700.jpg Photo Gallery