As if to add insult to injury, the explosion came to light only after analysts from the United States government and an international nuclear weapons monitor detected it and told the Argentines. Vessels from the United States, Britain, Brazil and Chile have been combing the seas as part of the search; the Argentine Navy’s four P3-B maritime patrol aircraft have been grounded and unavailable for deployment, according to Jane’s Research.

While the Navy did not formally give up hope of finding the crew, relatives began referring to their loved ones in the past tense. If the sailors perished, it would be the deadliest submarine catastrophe since 2003, when a Chinese submarine suffered a systems failure that killed 70 sailors, and the Argentine military’s largest loss of life since the Falklands War of 1982.

The disappearance and likely loss of the vessel, the San Juan, could turn out to be the greatest national tragedy to unfold under President Mauricio Macri, who came into office nearly two years ago vowing to invest in Argentina’s underfunded armed forces.

Even before the latest news, frustration at Mr. Macri had been mounting.

“Instead of spending on other matters, why don’t you spend on something truly important, like the life of all our relatives,” an unidentified woman asked Mr. Macri on Monday when he traveled to the resort city of Mar del Plata, according to a video of the meeting that was posted online.

Using submarines that have been in commission since the early 1980s “is taking a gamble on the life of our people,” she said.