“We are deeply saddened by this tragic incident,” said Col. Christopher Bronzi, commanding officer for the 15th Marine Expeditionary Unit.

One U.S. Marine has died, another is in critical condition and a rescue operation is underway for eight more after a training exercise "mishap" with an amphibious assault vehicle off the coast of Southern California on Thursday.

The deceased Marine, whose name is being withheld for 24 hours so that the family can be informed, was pronounced dead at a hospital in San Diego on Thursday, according to a press release early Friday by the I Marine Expeditionary Force.

The Marine in critical condition and another injured Marine in stable condition were taken to hospitals for treatment.

Fifteen Marines and one sailor were inside the vehicle for the training exercise near San Clemente Island on Thursday, when they reported taking on water at about 5:45 p.m., the release said. Read more at NBC News