With every hour, their chances of seeing their loved ones alive slipped away.
On Thursday, the announcement that an explosion was recorded near where the ARA San Juan submarine vanished meant that the anguished wait for families of the crew was all but over.
For some, sorrow turned to anger.
The Argentine navy's report to the relatives could not be concluded because many relatives became frustrated with the spokesman when he mentioned the reported explosion.
There were struggles and some family members voiced their anger at him.
Even before the confirmation of the explosion, the frustration of family members was boiling over.
Elena Alfaro, whose brother Cristian Ibañez is among the crew, said: "I feel like I'm waiting for a corpse. I feel like I'm at a wake. I also feel time passing and time is crucial. I don't want to bury my brother."
More than 200 relatives, many of whom have come from other parts of Argentina, have been sleeping at the base. It is here that the worst maritime crisis to befall Argentina in decades takes on a human face.
"At the moment there is only anxiety here. It's the worst thing I've had to face."
He said the relatives had suffered three "hard blows" in the wait: The submarine not coming back at the scheduled time; when satellite calls turned out not to have been from the sub; and previous noises heard in the area, which were not from the submarine.
With the chances of finding the crew alive reduced by the day, the relatives held prayer sessions at the base and were helped by psychologists.
But these small breaks in routine do not disguise the fact that this is a waiting game - and despair is close for many.
"There are times when I don't want to be alive," the mother of one of the sailors told El Pais via the Whatsapp messaging service (in Spanish).
"It will pass."
The frustration and anger erupted with the announcement of the explosion.
While navy spokesman Capt Enrique Balbi addressed journalists in Buenos Aires, in Mar del Plata feelings among the relatives were agitated.
Some wept while others tried to provide restraint.
The Argentine newspaper, Clarin, reported that a man shouted: "They killed my brother... They killed my brother because they sent them out to sea (in a vessel put together with) wire".
Some relatives say the navy was too slow to respond when the submarine lost contact with land, and wasted time before calling in international help.
The siblings of Cristian Ibañez were among those to express anger.
One asked why the authorities were using boats to look for a submarine, and another said the navy "lost crucial hours" by not treating the situation seriously enough at the beginning.
Ms Alfaro said: "I don't want to hear how many boats and aeroplanes there are. I want them to tell us where our relatives are."
Some of those who are missing relatives are too young to know what is happening. Beatriz Gambazza, who leads a creche at the naval base, said two of the children there have fathers on board.
The search for the sub has gripped Argentina, and people have come to the base to pin messages of support on a wire fence - it is both an emotional outpouring and a collection of prayers.
Bishop Gabriel Mestre, who has been attending the naval base, said: "Prayer doesn't only contain hope - it also includes strength to confront the most dramatic scenario."
In an emotive interview with the Argentine radio station, La Red, Luis, the father of Lt Cdr Damián Tagliapietra, was asked if he had heard anything about his son's status .
"Yes, yes, yes. Finally, yes. They have told us that they are all dead," he said.