Sentinel Ships From right, the Royal Australian Navy frigate HMAS Ballarat, the guided missile destroyer USS Spruance, and the guided missile cruiser USS Mobile Bay sail in formation in the Persian Gulf, Jan. 16, 2019, during Intrepid Sentinel, a multinational exercise designed to enhance warfighting readiness. SHARE IMAGE: Download Image: Full Size (1.34 MB) Tags: Navy Photo By: Navy Petty Officer 2nd Class David A. Brandenburg VIRIN: 190116-N-UD522-0019C.JPG Photo Gallery