At an unclear period there was an effort by coupist admiral Heck to acquire two submarines, but one had no crew and another missing parts.

Meanwhile in Urca, through dawn Mamede persuaded other military schools to his side. One notable reluctance was the Communication School's commander, who refused to hand him even a few radios. In time the São João Fort at the tip of the peninsula also joined. It'd been under orders to fire at any rebel warship trying to move, though as coastal artillery it was actually useless from technical failure.

At 07:00 in the morning 28 ECEME officers in private cars infiltrate into the Copacabana Fort. Liutenant Colonel Arídio Brasil already wanted to switch sides and just had to wait for his friend Kruel to move first and then for this reinforcement to compensate his sergeants, whom he distrusted. The Coastal Artillery HQ, right next to the Fort, remained legalist. They just lived with each other. When general Moraes paid a visit to the HQ, he had to cross a rebel platoon. The lieutenant had gotten his post thanks to Moraes and after a very awkward moment he was allowed in.
Moraes left at 10:00. He still had the HQ, the Duque de Caxias Fort and the 8th Motorized Coastal Artillery Group. He reinforced the HQ with a battery from the Duque de Caxias Fort and 100 men from the 8th Motorized, but somehow a Liutenant Colonel from the HQ, sent the latter away.

Goulart was getting bad news. Resistance among the admirals had immobilized Aragão's marines. Army Police and Presidential Guards, warned Âncora, were not enough muscle to hold the city. Though this shift in the Navy is critical, I've found no specifics on it other than the leading admiral. The IInd Army and 1st Infantry Regiment had defected. Late in the morning he was informed that if the rebels formed a government of their own, they'd receive American recognition. And very late his Minister of War gave him an ultimatum to break with the left, had it refused and resigned.
At 12:30 he left for Brasília. Which of the events motivated him is mostly speculation, but he informed Brasília of this decision at 09:00 and might've taken it at dawn. I think it was mainly Kruel's betrayal.

At the same time as he headed for the airport, generals Aguiar and Muniz Aragão met. Aguiar was attempting to usurp the 1st Infantry Division for himself, Muniz Aragão, the Aeroterrestrial. Inside the Vila Militar there was utmost tranquility. It had:
1st Infantry Regiment: One battalion
2nd Infantry Regiment: Left quarters
Infantry-School Regiment: Possibly one battalion
Andrade Neves Regiment (cavalry): Present
General Osório was in control. Any attempt at seizing the HQ would be met with violence. It was the same in the Aeroterrestrial. The Armored was also insensitive. Costa e Silva and ECEME wanted to usurp commands and encourage defections but the city's garrison was completely impervious. It did not really help the government, either. It just quietly stood in its quarters.
Hence the point of invading from Minas Gerais and São Paulo was to bring part of it far from the high commanders' grip. Only far away defections were highly successful.