The Marine Corps put an assault amphibious vehicle (AAV) back in the water this week for the first time since one sank last summer, killing nine service members, Marine Corps officials told Insider Thursday.

Last July, an AAV assigned to Bravo Company, Battalion Landing Team 1st Battalion, 4th Marines, part of the 15th Marine Expeditionary Unit, sank off the coast of California as it returned to the amphibious transport dock USS Somerset from San Clemente Island.

The mishap vehicle was carrying three AAV crewmembers, 12 Marines, and one Navy corpsman. Eight embarked Marines and the Navy sailor died, making this incident the deadliest AAV training accident in the vehicle’s history.

“Out of precaution, before we understand what caused this, we are pausing the waterborne operations for amtracs,” Marine Corps Commandant Gen. David Berger said the day after the accident, as the Corps was still searching for the bodies of the deceased, considered only missing at that point.

A recently released investigation into this tragic disaster revealed it was preventable. The accident was caused by a series of human and mechanical failures. Specifically, the vehicle was improperly maintained, training was inadequate, and critical safety procedures were not followed.

Responsibility for the deadly accident was placed on leaders across the chain of command, from the 15th MEU commander down to the vehicle commander. Disciplinary action has already been taken against some unit commanders.

AAV Training
Marines drive an AAV into the water during training at Camp Pendleton, California. (Photo by Lance Cpl. Alison Dostie/U.S. Marine Corps)

This week, after an eight-and-a-half-month pause, AAVs again started splashing, but with conditions, Corps officials said.

Last Friday, the Marines published requirements for the resumption of AAV waterborne operations, Marine Corps spokesperson Capt. Andrew Wood told Insider on Thursday.