"It wasn't until two years later, after an exhaustive analysis of the pattern of his raids had given us enough material to work with, that we determined that he must have found an opening into one of the tunnels up here in the game preserve." He gestured again at the map. "Very likely he immediately saw that no human being had been down there in a long time and that there wasn't much chance of a man coming down there in the foreseeable future. It was a perfect place for his base."
"How does he move in and out?" Stanton asked.
"This way." The colonel traced a finger down one of the red lines on the map, southward, until he came to a spot only a little over two miles from the southernmost tip of the island. The line turned abruptly toward the western shore of the island, where it stopped. "There are tunnels that go underneath the Hudson River at this point and emerge on the other side, over here, in New Jersey. The one he uses is only one of several, but it has one distinct advantage that the others do not. All of them are flooded now; the sun bomb caved them in when the primary shock wave hit the surface of the water. The tunnel he uses has a hole in it big enough for him to swim through.
"In spite of his high rate of metabolism, the Nipe can store a tremendous amount of oxygen in his body and can stay underwater for as long as half an hour without breathing apparatus, if he conserves his energy. When he's wearing his scuba mask, he's practically a self-contained submarine. The pressure doesn't seem to bother him much. He's a tough cookie."
"I'll remember that," said Stanton somberly. "I won't try to race him underwater."
"No," said Colonel Mannheim. "No, I wouldn't do that if I were you."
They both knew that there was a great deal more to it than that. In spite of the near miracle that the staff of the Neurophysical Institute had wrought upon Stanton's nerves and muscles and glands, they could only go so far. They could only improve the functioning of the equipment that Stanton already had; they could not add more.
His lungs could be, and had been, increased tremendously in efficiency of operation, but the amount of air they could actually hold could only be increased slightly. There was no way to add much extra volume to them without doing so at the expense of other organs. In a breath-holding contest, the Nipe would win easily, since his body had evolved organs for oxygen storage, while the human body had not.
You cannot make a silk purse out of a sow's ear if you are limited to the structures and compounds found in sows' ears. The best you can do is make a finer, stronger, more sensitive sow's ear.
"I understand that the Nipe has his hideout pretty well bugged with all kinds of alarms," Stanton said. "How did you get your own bugs in there without setting off his?"