Hell Raider — Ramsay Thorne

Flesh-eating demons wait for Captain Gringo on the Amazon!
On the nightmare rivers of Brazil where piranhas and naked cannibals vie for the taste of human flesh, there are now far worse predators. Border bandits have seized control, raping and murdering the local populace. No sane man would want to lead a gunboat into that slimy, snake-infested hell, especially when a certain redhead with emerald eyes, and a slit up the front of her skirt has been waiting for him to give her the attention she needs.
But Captain Gringo's got no choice. He's got a price on his head and if he refuses the assignment the shaky Brazilian government has in mind, he'll get a bullet between the eyes. So he heads upstream, unaware and unprepared for the international conspiracy waiting to blow him to kingdom come.