Zircon waved his hand. "The method was developed by our young Mr. Brant, who sometimes shows slight sparks of intelligence. He has a device which projects infrared light, and gla.s.ses that allow the wearer to see whatever that light illuminates."

Rick stared. Zircon was proposing that they take his underwater camera and use it for illumination. That must mean ... "You want to swim over with the lungs?" he asked incredulously.

"And why not?"

"But we've never done any night diving!"

"You tested the camera at night, did you not?"

"Yes," Rick admitted, "but that was in water that we knew, off Pirate's Field at home. And we only stayed in long enough to expose a few feet of film."

"We know enough about these waters to know that there are no dangerous obstructions beyond the reef, at least between here and the _Maiden Hand_."

Scotty laughed. "This is a day I never thought would come. It's usually the other way around, with Rick trying to sell some idea that everyone else opposes. Why not swim at night, Rick?"

"No reason," Rick admitted. "It was just that it hadn't occurred to me.

There's one difficulty, though. I have only two pairs of gla.s.ses with infrared-sensitive lenses. So only two of us could go."

"Only two could dive with the camera," Tony corrected. "But all of us could go. Two would remain on the surface, with the floats, in case of trouble."

"Who would dive and who would stay on the surface?" Scotty demanded.

Rick produced a quarter. "Let coins decide. Except for the professor. He thought of it, so he dives."

"Fair enough," Scotty agreed. "All right with you, Tony?"

"Of course. The three of us, then. Odd man goes with Hobart."

Tony and Scotty produced coins. With Rick, they walked into the living room and lighted a kerosene lamp.

"Now," Rick said, and tossed his coin, catching it in the palm of his hand and slapping it onto his other wrist. Tony and Scotty followed suit. Rick uncovered first. He had heads. Tony uncovered and displayed a tail.

Scotty groaned. "Shucks! I lose. It's one of you."

Rick held his breath as Scotty uncovered--another tail! He turned to Zircon. "We dive, while Scotty and Tony stay topside."

"Good. Well, what are we waiting for?"

They changed quickly into trunks, then a.s.sembled their diving gear. Rick took the front plate from his camera and put the infrared searchlight on its mounting bracket. He changed to a fresh battery, then replaced the film in the camera with the special infrared-sensitive film.

Whatever the infrared illuminated could be seen through special gla.s.s.

Rick had ordered lenses ground from the gla.s.s and had placed them in frames made to fit into a face mask. These frames could be purchased at any diving-equipment supply house. They had been designed for divers who had to wear their own corrective gla.s.ses, and they suited Rick's purpose to perfection. He handed a pair to Hobart Zircon, then inserted the other pair in his own mask.

Zircon, Tony, and Scotty decided to take spear guns. Zircon chose Rick's rubber-powered gun, while Tony selected the light spring gun. Scotty chose the highest-powered gun they had, a new jet-type powered with carbon dioxide.

Rick and Zircon connected their regulators to two freshly filled tanks, then tested the equipment. Zircon tied a rope to his belt.

The big scientist drew them together for a brief conference.

"We'll swim out and cross the reef," he directed. "Then we'll swim along the reef, staying as close as possible to the breakers. They will help conceal us. When we approach the boat, Tony and Scotty will stop and hold position. Scotty, are the binoculars waterproof?"

"Yes, they are."

"Then take them. Rick and I will go directly to the bottom at the base of the reef. We will then proceed along the reef until we spot our friends yonder."

Rick had an unhappy thought. "Suppose they see us?"

"We will try to prevent them from seeing us. However, if they do, I suggest a retreat in as good order as we can manage. If they should catch up with us, we will bl.u.s.ter and bluff our way on the basis that we were only diving to see if they were trying to search our wreck."

Scotty laughed. "Turn their own table on them. That's very good, Professor."

"I'm glad I'm not a physicist," Tony said piously. "We archaeologists aren't half so devious."

"I am acting in my capacity as a former consultant to JANIG, and not as a physicist," Zircon retorted with dignity. "You will refrain from casting aspersions on my profession, Doctor Briotti."

"My apologies," Tony said, grinning. "In other words, the man is devious, but the scientist is not."

"Exactly. Well, shall we go?"

Rick was glad to get into the water. The camera in its underwater case was heavy in air, but weighed only a few ounces in water. He swam with face mask under, breathing through his snorkel and letting the camera hang.

They crossed the reef without difficulty, then turned to swim along it.

The trough just seaward of the breaking point of the waves was the most comfortable swimming position and they went in single file, Zircon leading.

Every now and then Rick looked up. They were getting near the boat, he thought. Perilously near. The boat was anch.o.r.ed just inside the reef, and he could see activity on its deck. Apparently the frogmen had returned from their first dive and were changing tanks.

Zircon stopped swimming and lay motionless in the water. Rick drew abreast of the big scientist, and Tony and Scotty stopped behind them.

As they watched, suited figures with belt lights and back tanks climbed down a ladder into the water. A third man, on deck, lowered something to them. It was hard to see, but Rick thought it had a golden glisten and that it was round, about the size of a basketball. The frogmen took it and went under.

[Ill.u.s.tration: _A third man lowered something that glistened like gold_]

Zircon's big hand took Rick by the shoulder, then he turned and motioned to the others that they were going under. Rick shifted from snorkel to aqualung mouthpiece. He took the end of rope that Zircon held out and snapped it to his weight belt. He and Zircon were now connected by a ten-foot length of rope, necessary to keep them from becoming separated in the darkness.

He submerged and dove straight down into the blackness. His thumb compressed the b.u.t.ton on the side of the case and the camera started, the infrared light turning on. A narrow cone of water extending out about twenty feet was illuminated, but the illumination was visible only through the special gla.s.ses he and Zircon wore.

Rick held the b.u.t.ton until they reached bottom, then suddenly realized he would use all his film before they had even found the frogmen. He groaned silently. Why hadn't he used his head? The light as well as the camera motor were operated by the same b.u.t.ton. If he had only thought, it would have been a few seconds' work to change the circuit so the light would be on continuously. Or he might even be able to rig a waterproof switch that would operate just the light.

Well, it was too late now. He jerked on the rope for Zircon to stop, then took his belt slate and wrote, "Cam on whn lite is. Wll use nw & thn." He held it in the beam of infrared light for Zircon to read. The scientist scribbled "OK" under the message, then gave him a gentle push as a signal to go ahead.

Rick held his wrist in the beam and read ninety-two feet on his depth gauge. He calculated quickly. They would have enough air for about twenty-five minutes at this depth.

He held the camera switch long enough to see that there was only smooth bottom ahead, then released it. Almost total blackness flooded in. For all practical purposes it was completely dark, no glimmer of light to mark their way.

For an instant Rick felt panic, but reason rea.s.serted itself. It was instinctive to feel fear under such circ.u.mstances, he thought. Not only was he out of his own medium, air, but in a high-pressure realm inhabited by potentially dangerous creatures. He grinned inwardly at the thought. The most dangerous creatures in this vicinity were human.

A twinkle of light stopped him, but Zircon continued on and the connecting line tightened. Rick identified the twinkle as phosph.o.r.escence from some marine creature on the reef. There were many such in the ocean. He flashed the infrared light, saw that they were still heading properly, and cut it off again.

The rope at his belt tugged four times for danger! He stopped instantly, letting go of the camera with one hand while he reached for his belt knife. Then he saw what Zircon had seen, a glow in the water ahead and above them. Rick estimated quickly the distance they had traveled. There was no doubt of it. The frogmen were at the octopus cave!