"How often do they have to come up?" George asked.

"Oh, I'd say the crocs come up about once every hour. It depends on the water temperature. The warmer the water, the more often they have to breathe. In cold water they can hibernate a lot longer."

"Do they have to surface to eat?" a man inquired.

"Yes. They can seize their prey underwater, because they have valves in the backs of their throats that close when they open their mouths and the water can't flow into their lungs. But they have to stick their heads out to swallow."

The group walked on, and Nancy asked the guide, "What do you do with all these crocodiles?"

"The Ecology Company sells them to various zoos and parks and even to the government," he replied.

"The government?" George repeated. "What would Uncle Sam do with a lot of crocodiles?"

The guide told her they were distributed to certain areas, "You have probably heard that the crocodile is a vanishing species. We are trying to do our part in seeing that American crocodiles do not become extinct."

At this remark Bess heaved a great sigh, "Would America really be badly off if it didn't have any?"

The guide looked at her with contempt in his eyes. "Young lady, if you knew anything about ecology, you would realize how useful they are!"

Bess had no chance to reply because a loud bell rang.

"This is an alarm!" the guide exclaimed. "I must ask you all to get back to the dock as quickly as possible and leave the island!"

"Why?" Nancy asked, disappointed, "Does it mean a crocodile is loose?"

"It could be," the guide replied. "Now please, ladies and gentlemen, return to your boats without delay!"

The tourists ran. Bess was one of the first, and the others, for once, had trouble keeping up with her. Just before they reached the skiff, a guard at the dock asked them if they had registered when they came in.

"No, we forgot," Danny said. "I'll do it now." He hurried into a small office building and signed his name. Then he entered the girls' names as Anne, Elizabeth, and Jackie Boonton.