Carnahan was (presumably) the first mate of the Petrox Explorer. An extremely levelheaded, likable individual, he went with Jack Prescott when Jack took out a search party into the jungles of Kong Island to rescue the kidnapped Dwan from the clutches of King Kong. Midway through their trek the group had the misfortune to catch up to Kong while Carnahan crossed a log bridge over a deep canyon along with Joe Perko, Timmons, Garcia and Boan. Kong, enraged when the sailors shot at him, grabbed his end of the log and proceeded to shake them all off. Only Boan survived, and Carnahan was the last of the men to fall their deaths.
Possibly a reference to the 1976 King Kong, a sailor named Carnahan is part of the search party trying to get Ann Darrow back from Kong. However Carnahan's name is only given in the novelization by Christopher Golden, and the scene in which he is killed by a piranhadon was cut from the film but restored for the Extanded Edition DVD.