Outside the base 400 kilometers (250 miles) south of Buenos Aires, the mood was tense but still somewhat optimistic.
Ships and aircraft from seven countries are searching 24 hours a day through storms that have continued to rage at sea. And still, they have brought none of the news relatives want.
"Courageous Men and Women of the Navy: Our Hearts have Stopped Beating Until You're Home," read one banner, carefully handwritten.
Most of the crew live in this seaside South Atlantic city.
Many hail from distant provinces, like Eliana Krawczyk, from Misiones in the north. She is South America's first female submariner.
About 100 relatives of the missing were at the base getting crisis medical and counseling support, around the clock. They tried to stay calm and keep hope alive.
"Be strong Daddy. Your family is waiting for you," read one sign, alongside religious posters and some handwritten prayers.
Anxiety is deepening
"People's moods are pretty good. Of course some are more upbeat than others. But there is a general feeling that at any time, something positive could happen," said Jorge Villarreal, the father of crew member Fernando.
Media are not allowed on the base.
And only some relatives come. Some stop, take pictures, leave messages and head off on the avenue outside the base.
President Mauricio Macri met with them to try to rally spirits.
"So far, we have not had a lot of crisis reactions, such as weeping; people are sort of stable amid the uncertainty," said therapist Enrique Stein.
But "anxiety is starting to grow," he stressed.
Search efforts have been hampered by inclement weather, including a powerful storm that has whipped up waves reaching seven meters (23 feet) in height.
A multinational air and sea search team is focusing on an ocean patch about 300 kilometers in diameter, radiating from the last point of contact.
The submarine had been returning from a routine mission to Ushuaia, near the southernmost tip of South America, to Mar del Plata.
It is one of three submarines in the Argentine fleet.
Sixty-five meters long and seven meters wide, it was built by Germany's Thyssen Nordseewerke and launched more than three decades ago.
It underwent a refit between 2007 and 2014 to extend its use by about 30 years.
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