The USS San Diego steams off the coast of Marine Corps Base Hawaii, July 14, 2016 (Aaron Patterson/U.S. Marine Corps)

Pfc. Isaac Romero had completed his first year as a Marine the day before he drowned Sunday just off a beach on the Hawaii base where he was stationed, the Marine Corps said Wednesday.

Romero, 22, a Minnesota native, was assigned to Marine Wing Support Squadron 174 at Marine Corps Base Hawaii on Oahu in December after completing training as a combat engineer, according to a Marine Corps news release.

His death prompted the base commander to temporarily close several of the base's beaches beginning Wednesday to conduct a review of beach safety procedures and risk management practices, the Marine Corps said.

They will remain closed until Wednesday.

Romero was swimming in the afternoon from North Beach on the base, leaving a friend behind on land.

He had swum out about 60 yards before the friend lost sight of him, the Marine Corps said. The friend called the base Provost Marshal's Office at 2 p.m., and first responders from the base and Honolulu Fire Department soon arrived.

They found his body in shallow water about 45 minutes later. He was pronounced dead at 3:42 p.m. at Castle Medical Center, the Marine Corps said.

The Naval Criminal Investigative Service and local authorities are still looking into Romero’s death.

“Our heartfelt sympathies and deepest condolences go out to Isaac's family and friends, and we join them in remembering and mourning this Marine,” Lt. Col. Gideon Grissett, commander of Marine Wing Support Squadron 174, said in the news release.

"His enthusiasm and devotion to duty inspired others with his positive, upbeat attitude. We are grateful to have had the opportunity to know him and be a part of our Marine Corps family."

A memorial service is planned for May 6 at the base chapel.