"What do you see?" asked Frank, nervously.
"It is the Shark, all right," was the reply, "and she is backing off.
She may be going to ram us."
"Then it's us for the bottom," cried Frank.
"Why the bottom?" asked Jimmie.
Frank did not answer for a moment. He was still standing back of the little fellow and looking over his shoulder, out of the glass panel.
"Because," he said, "the Shark takes chances in bumping us at a considerable depth. She is higher than we are, and her prow sits a great deal above our vulnerable parts. If she strikes us when we are nestling on the bottom, her blow will glance off."
"If she knows it, then," Jimmie said, "she won't follow us down. What will she do?"
"Chase herself off."
"I hope so!" cried Jimmie.
"It beats the Old Scratch why Ned and Jack don't come," Frank said, presently. "I'm afraid something has happened to them."