Darwin's Secret — Richard Hoyt

This is a wild, picaresque adventure story of a riverboat trip deep into the heart of the Amazon basin. When the exotic riverboat Barco Igaranha casts off from Belem, her passengers cannot possibly imagine what awaits them on the river. Nicholas Bodan, a broke American writer, and Hanna Doherty, a fugitive doctor, are headed for the gold rush at Loucofilho; Father Ferrua, a Catholic priest, and Mae Janaina, a high priestess of Brazilian voodoo, on the other hand, are after Obatala's Fish, a priceless, supposedly miraculous religious icon rumored to be hidden somewhere on board the Barco Igaranha.