SS-15 Salt Water Crocodile

Ranchers in Texas along the Gulf of Mexico are in an uproar. They are losing valuable livestock, mostly calves and colts, in the gulf. No, the animals are not falling into the water and drowning. These young and small animals are being killed by creature in the water. The ranchers suspect an alligator is to blame, but alligators live in fresh water not salty. The ranchers go to the local game warden, but this fellow is either too tired or too lazy to get to the bottom of the problem. And this fellow won't let the ranchers hunt down this livestock killer. The ranchers are ready to revolt. They plan to find and kill the killer with or without the game warden's permission.
How does Sam figure into the ranchers' problem? He and the Porpoise crew are out on the ocean, and the crew doesn't even know where they are headed or if they are headed anywhere in particular.