The Seabed Constructor, owned by the company Ocean Infinity, will set out Friday from the port of Comodoro Rivadavia, some 1,800km south of Buenos Aires, carrying both Argentine sailors and relatives of the missing submariners.

“We feel this is the last opportunity to find them. And we want to find out what happened,” said Luis Tagliapietra, whose son Alejandro was a lieutenant on the San Juan.

Ocean Infinity was also assigned the task of searching for flight MH370 which vanished without trace in March 2014 en route from Kuala Lumpur to Beijing.

The government of President Mauricio Macri has declared that there were no survivors from the San Juan, but exactly what happened to the missing submarine in the waters of the South Atlantic has remained unclear.

Investigators suspect a technical fault occurred when the vessel lost contact some 450km off the coast of Argentina as it was heading back to its base in the southern port of Mar del Plata.

The Seabed Constructor is equipped with cameras that can be submerged to a depth of 6,000m. If it finds the missing sub, it will receive a reward of US$7.5 million (RM31.13) million).

Families of the missing crew have kept up pressure on the government not to give up on the search, staging protest marches and camping out in front of the parliament.