The rapid-response unit was unveiled by officials after an attack in which 11 heavily armed thieves stormed a passenger boat heading for the state capital, Belém.
Joao Bosco Rodrigues, head of Pará's specialist police divisions, said the unit was "another instrument to combat and prevent" the actions of pirates in the Amazon region. "This group will be there to react to any kind of demand on our rivers," he said.
Witnesses to the latest attack said that thieves in small motorboats approached the passenger vessel, firing into the air, on Tuesday afternoon.
Once aboard, the men reportedly threatened to execute some of the estimated 140 adult and child passengers.
"They humiliated everybody," passenger Artur Cesar told the local Diário do Pará newspaper. "They put guns to the children's heads and even said they would cut the fingers off those who didn't hand over their rings. There were pistols, revolvers – lots of weapons."
Benivaldo Carvalho said he had been hit on the head by the pirates. "It was two hours of terror, humiliation and powerlessness. They pointed their guns at us and said they were going to kill us."
Another passenger, Maria das Gracas Monteiro, said: "They treated us worse than dogs. I thought I wouldn't make it back alive."
The issue of piracy in the Brazilian Amazon made international headlines in 2001, following the murder of Sir Peter Blake, a world famous sailor and environmentalist who was shot by a gang known as "the water rats" while on a research expedition to the region.
Local boatmen say attacks are now common in Pará, a sprawling, sparsely-policed region.
In March this year a sailor in his 20s was killed when two boatloads of pirates raided his vessel as it transported acai fruit to Belém.
Last month two more sailors were shot by pirates in the neighbouring state of Amazonas. Police blamed a group known as the "Black river pirates".
Paulo Cesar Pantoja, the owner of the boat attacked on Tuesday, said numerous attacks had taken place in recent months.