The Marines called off a search for eight troops who went down with their landing craft off the coast of Southern California during a training exercise on Thursday. All eight are presumed dead, the Marine Corps confirmed Sunday. Eight other marines on the 26-ton amphibious assault vehicle were rescued, though one died later in the hospital and two remain in critical condition. The massive tank-like craft sank quickly in deep water, hindering search efforts. “It is with as heavy heart that I decided to conclude the search and rescue effort,” Col. Christopher Bronzi, of the 15th Marine Expeditionary Unit, said Sunday. All of the troops were with the 15th Marine Expeditionary Unit, at Camp Pendleton, north of San Diego.