U.S Navy divers search for objects used to simulate mines during a multi-agency training exercise in the Piscataqua River during a Frontier Sentinel exercise.

PORSTMOUTH, N.H. (Jun. 10, 2008) U.S Navy divers search for objects used to simulate mines during a multi-agency training exercise in the Piscataqua River during a Frontier Sentinel exercise. The annual maritime homeland security exercise involves the Canadian Navy and the U.S. Navy and Coast Guard, as well as numerous other federal, state and local agencies in the detection, assessment and response to maritime security threats. U.S. Coast Guard photo by Petty Officer Seth Johnson File# 080610-G-6464J-001