Seven US Marines and one sailor, missing since a training accident off the California coast Thursday, are presumed dead, according to the military.
The announcement came as a 40-hour search and rescue effort was canceled.
The service members were aboard an Amphibious Assault Vehicle (AAV) that sank during the exercise.
Eight other Marines were rescued after the crash, but one later died. Two others are in critical condition.
“It was with a heavy heart that I decided to conclude the search and rescue effort,” said Col. Christopher Bronzi, commander of the 15th Marine Expeditionary Unit (MEU).
A search operation involved helicopters and ships over an area of more than 1,000 square nautical miles (3,439 km2), the marines said in a statement.
The AAV was back on the amphibious warship USS Somerset after operating on San Clemente Island when it started to take in water and sank, military officials said on Friday.
The Marines often practice beach assaults in the area.
Colonel Bronzi said the effort would now be shifted to one aimed at locating the bodies of the missing.
The 15th MEU, based at Camp Pendleton, near San Diego, has approximately 2,200 personnel and conducts maritime rapid reaction, conventional amphibious and other operations.