It disappeared off Argentina's coast a year ago in the middle of its journey from Ushuaia to its homes base, Mar del Plata.
Officials lost radio contact with the San Juan on November 15, 2017, and the Argentine navy called off its rescue operation about two weeks after they were unable to locate the ship, saying there was "no chance of survival" for its crew with just seven days of oxygen aboard. "For us this is the start of a new chapter".
All the while, relatives and family members of the missing 44 crew-members pressured the Navy, the Defense Ministry and the Cabinet to continue the search.
Last August, Argentina's government hired Ocean Infinity to search for the wreckage, with a promised $7.5 million payout if the submarine was found.
Aguad said: "Much of what happens from here will have to be resolved by the justice department".
Argentina's president Mauricio Macri said the families of the submariners should not feel alone and delivered an "absolute and non-negotiable commitment" to find "the truth".
The sub was ordered to cut its mission short and return to the naval base in Mar del Plata immediately.
Facebook down: Social network goes dark
Several subscribers took to Twitter on Monday afternoon to complain that they could not log into their account. Here's the message users receive when they try to visit Facebook on November 12, 2018 , at around 1 p.m.
Family members at the navy headquarters were shown three images of the remains of the San Juan's "sail", or tower, and bow sections. Federal police raided naval bases and other buildings last January as part of an investigation, soon after the government dismissed the head of the navy.
Experts have said that refits can be hard because they involve integrating systems produced by different manufacturers, and any mistake during the cutting phase can put the safety of the ship and crew at risk.
Argentina gave up hope of finding survivors after an intense search aided by 18 countries, but a few navy units have continued providing logistical support to Ocean Infinity. The captain later communicated that it had been contained.
It was only several days into the tragedy that Navy officials acknowledged the old, German-built submarine had reported a problem with its batteries in its final communication on November 15.
Teams will dive down to whatever is left of the San Juan during an operation that is expected to last about seven hours, but defence minister Oscar Aguad has warned that the country "does not have the means to recover the wreckage".
The search crew, composed of 40 specialists from Ocean Infinity, set sail on September 8 after winning a bid in August to take up the search effort. The company had previously been contracted to find Malaysia Airlines Flight 370, which disappeared over the Indian Ocean in 2014.