Perhaps the professor can be excused for hurrying through with his meal, as he was anxious to get down to the surface of the sea. Jerry, too, wondered how his new attachment would work when there was a swell on, for, up to now, he had only tested the hydroplanes on comparatively smooth water.

“Well, here we go,” he announced, when, after getting up from the table, they had all gathered in the pilot house ready for the descent. “Ned, you take charge of the air rudder, will you? And Bob, you stand here ready to throw in the gears of the water propeller when I give the word. I’m going to stand by the hydroplane lever.”

“Is there anything I can do?” asked the professor eagerly. “I’d like to help.”

“Oh, I guess we can manage,” replied Jerry. “Pull the depressing handle, Ned.”

The merchant’s son yanked the lever toward him. Almost instantly the Comet pointed her nose toward the ocean that rolled below them. The boys were now practically out of sight of land.

Professor Snodgrass, seeing that he could be of no service, again took up his telescope to scan the water for a possible sight of some fish specimen, though he did not hope to so soon get the prize he sought.

“We’re almost down,” murmured Ned, who was keeping watch through a glass window in the floor of the pilot house.

“Yes,” agreed Jerry. “Now, Ned, stand ready to haul up on the bicycle wheels when I give the word.”

The three boys were on the alert. Would the new attachment work on the ocean? They were all anxious to know.

“Now, Bob and Ned!” called Jerry suddenly.