The former BRP Miguel Malvar (PS-19), which was supposed to be sunk as part of a Balikatan missile exercise, submerged while being positioned off the coast of San Antonio, Zambales on Monday morning, May 5.br br No gunfire was heard nor missile was fired but the BRP Miguel Malvar descended to the bottom of the ocean floor as it took on water while being towed to a designated location approximately 30 nautical miles west of San Antonio town at around 7:20 a.m.