Mark Harris has gills in his neck to extract oxygen from the water. He is able to breathe air for up to 12 hours at a time, but must return to an underwater environment after that time.
The Cetacean does not carry missles or weaponry of any kind. Rather, it is an ocean-going laboratory for conducting tests and surveys, and is equipped with scientific equipment of all kinds.
Oceanography * Navigation
Foundation for Oceanic Research
Mark Harris was found washed ashore on a Califomia beach, unconscious and with a bump on his head. However, lacking lungs and sporting a pair of gills in his throat -- not to mention webbed fingers and toes -- it was obvious to oceanographer Dr. Elizabeth Merrill that he was not quite human.
Taking him from the hospital where he'd been brought, and submerging him in the ocean, the woman revived the fish-man only to discover that he had lost his memory. Making occasional forays into the ocean, he eventually learned little more than that he is the last survivor of the underwater civilization of Atlantis.
With nowhere else to go, he stayed at the institute, working with Dr. Merrill and the crew of the subsea ship The Cetacean to learn more about the oceans and to fight crime on the high seas -- crimes which included the kidnapping of a mermaid, hi-tech underwater gear going mad, and the nefarious doings of the evil Mr. Schubert.