“Probably by boat,” Mr. Jamison said.
“The Coast Guard keeps close tabs on all boating,” Mr. Evans said. “And the bay’s too shallow to allow ocean-going ships inside.”
A thought sprang into Eddie’s mind. “Mr. Evans,” he said, “I found a rubber strap on the beach last week. It looked like a strap broken off a swim fin or something like that. It—it has some foreign printing on it. I have it at home.”
His announcement had an immediate effect. “That should give us a real clue,” the FBI man said quickly. “It makes sense, too, that the cylinders would be recovered by skin divers. Perhaps foreign divers similar to our own frogmen.”
“It would have to be done after dark,” Mr. Ross said. “Otherwise they would be seen. And how could anyone locate a small cylinder like that under ten feet of water at night.”
“I think I can answer that,” Eddie’s father said. “In fact, Eddie and Teena found that answer. It could be located with a Geiger counter.”
“That’s it,” the FBI man agreed. “For instance, they could use a rubber boat to sneak in under cover of darkness. They would know the approximate location of the cylinder.”
“How?” Teena’s father asked.
“By some established plan. Probably by triangulation. They could use the lighthouse for one reference point. Perhaps some other signal light on shore would give them a second point.”
Quickly, Eddie told him about seeing the heavy-duty battery lantern in the shack. “They might use it for a signal light,” he said.