Submariners of the Gods (Doc Minus Two Book II)

What can sink a ship and disappear without a trace and is not a submarine? In the second novel in the Doc Minus Two series, this becomes a critical question when six fishing boats are mysteriously torpedoed in broad daylight, as if by an invisible predator. No one can determine who or what perpetrated the attacks, or where it came from. Both the U.S. and Mexican navies fail to find any signs that a submarine, a boat, a plane, or even a remote-controlled device was ever involved. The only hint is the existence of posters of an obscure Aztec god that are found floating in the water near all sinking sites. The gruff Doc Minus Two, a failed medical doctor turned detective, and his former client Al, an archeologist, travel to Mexico to investigate rumors of a tiny cult that seems capable of outmaneuvering modern naval powers.