The speedboat was submerged about 20m deep under the Itacoai river in the Amazon rainforest in northern Brazil with the help of six sandbags, authorities said in a press statement.
A third suspect has been arrested in connection with the deaths of British journalist Dom Phillips and Indigenous expert Bruno Pereira in Brazil, federal police said.
Two of the five suspects are brothers Oseney and Amarildo da Costa de Oliveira, who on Wednesday confessed to murdering the pair with a firearm and covering up their remains.
Local broadcaster CNN Brasil cited federal police sources, who claim a dental exam confirmed the remains found in remote jungle in Atalaia Do Norte belonged to veteran journalist Dom Phillips.