President Michel Temer and his elected successor Jair Bolsonaro attended the hours-long ceremony in a navy base in Itaquai, near Rio de Janeiro, that saw the 72-meter (236-foot) vessel slowly lowered into Atlantic Ocean waters.

Temer's wife Marcela Temer baptized the sub, called the "Riachuelo" after a 19th-century Brazilian naval victory against Paraguayan ships, with the traditional smashing of a bottle of champagne. It will now undergo two years of sea trials before entering service.

The fleet of submarines is to protect Brazil's 8,500 kilometers (5,300 miles) of coastline and territorial waters, which include deepwater oil fields vital for the country's economy.

Four of the new vessels, including the Riachuelo, will be diesel-powered and are all to be completed by the end of 2022.

One is to be nuclear-powered, giving it far greater range and the ability to stay submerged for long periods, but is now expected to be launched in 2029, six years behind schedule.

The vessels are being built as bigger versions of France's Scorpene-class of attack submarines under a 2008 deal agreed on condition that Brazil acquire the necessary technology -- except for the nuclear reactor in the last sub.

"It is a combination of French technology with the capabilities and resources of the Brazilian Navy -- a sort of 'tropicalization' (of the Scorpene) to protect our vast territory," said Andre Portalis, head of the ICN consortium building the subs.

Other countries have also chosen Scorpene-class subs to add to their navies, including Chile, Malaysia and India.

India has been rattled by leaks to an Australian newspaper of top secret information on the six Scorpene boats it is building. The French shipbuilder behind the sub, DCNS, has taken legal action to try to stop the leaks.

Australia has a deal with France to build 12 subs of a different sort -- Barracuda-class -- for its navy.