They stripped to swim trunks and pull-overs, then fastened on the harness of their breathing equipment. Don picked up one of the small but surprisingly heavy plastic cylinders and handed it to Franklin.
“These are the high-pressure jobs that I told you about,” he said. “They’re pumped to a thousand atmospheres, so the air in them is denser than water. Hence these buoyancy tanks at either end to keep them in neutral. The automatic adjustment is pretty good; as you use up your air the tanks slowly flood so that the cylinder stays just about weightless. Otherwise you’d come up to the surface like a cork whether you wanted to or not.”
He looked at the pressure gauges on the tanks and gave a satisfied nod.
“They’re nearly half charged,” he said. “That’s far more than we need. You can stay down for a day on one of these tanks when it’s really pumped up, and we won’t be gone more than an hour.”
They adjusted the new, full-face masks that had already been checked for leaks and comfortable fitting. These would be as much their personal property as their toothbrushes while they were on the station, for no two people’s faces were exactly the same shape, and even the slightest leak could be disastrous.
When they had checked the air supply and the short-range underwater radio sets, they lay almost flat along the slim torpedoes, heads down behind the low, transparent shields which would protect them from the rush of water sweeping past at speeds of up to thirty knots. Franklin settled his feet comfortably in the stirrups, feeling for the throttle and jet reversal controls with his toes. The little joy stick which allowed him to “fly” the torpedo like a plane was just in front of his face, in the center of the instrument board. Apart from a few switches, the compass, and the meters giving speed, depth, and battery charge, there were no other controls.
Don gave Franklin his final instructions, ending with the words: “Keep about twenty feet away on my right, so that I can see you all the time. If anything goes wrong and you do have to dump the torp, for heaven’s sake remember to cut the motor. We don’t want it charging all over the reef. All set?”
“Yes — I’m ready,” Franklin answered into his little microphone.
“Right — here we go.”
The torpedoes slid easily down the ramps, and the water rose above their heads. This was no new experience to Franklin; like most other people in the world, he had occasionally tried his hand at underwater swimming and had sometimes used a lung just to see what it was like. He felt nothing but a pleasant sense of anticipation as the little turbine started to whir beneath him and the walls of the submerged chamber slid slowly past.
The light strengthened around them as they emerged into the open and pulled away from the piles of the jetty. Visibility was not very good — thirty feet at the most — but it would improve as they came to deeper water. Don swung his torpedo at right angles to the edge of the reef and headed out to sea at a leisurely five knots.
“The biggest danger with these toys,” said Don’s voice from the tiny loudspeaker by Franklin’s ear, “is going too fast and running into something. It takes a lot of experience to judge underwater visibility. See what I mean?”
He banked steeply to avoid a towering mass of coral which had suddenly appeared ahead of them. If the demonstration had been planned, thought Franklin, Don had timed it beautifully. As the living mountain swept past, not more than ten feet away, he caught a glimpse of a myriad brilliantly colored fish staring at him with apparent unconcern. By this time, he assumed, they must be so used to torpedoes and subs that they were quite unexcited by them. And since this entire area was rigidly protected, they had no reason to fear man.
A few minutes at cruising speed brought them out into the open water of the channel between the island and the adjacent reefs. Now they had room to maneuver, and Franklin followed his mentor in a series of rolls and loops and great submarine switchbacks that soon had him hopelessly lost. Sometimes they shot down to the seabed, a hundred feet below, then broke surface like flying fish to check their position. All the time Don kept up a running commentary, interspersed with questions designed to see how Franklin was reacting to the ride.
It was one of the most exhilarating experiences he had ever known. The water was much clearer out here in the channel, and one could see for almost a hundred feet. Once they ran into a great school of bonitos, which formed an inquisitive escort until Don put on speed and left them behind. They saw no sharks, as Franklin had half expected, and he commented to Don on their absence.
“You won’t see many while you’re riding a torp,” the other replied. “The noise of the jet scares them. If you want to meet the local sharks, you’ll have to go swimming in the old-fashioned way — or cut your motor and wait until they come to look at you.”
A dark mass was looming indistinctly from the seabed, and they reduced speed to a gentle drift as they approached a little range of coral hills, twenty or thirty feet high.
“An old friend of mine lives around here,” said Don. “I wonder if he’s home? It’s been about four years since I saw him last, but that won’t seem much to him. He’s been around for a couple of centuries.”
They were now skirting the edge of a huge green-clad mushroom of coral, and Franklin peered into the shadows beneath it. There were a few large boulders there, and a pair of elegant angelfish which almost disappeared when they turned edge on to him. But he could see nothing else to justify Burley’s interest.
It was very unsettling when one of the boulders began to move, fortunately not in his direction. The biggest fish he had ever seen — it was almost as long as the torpedo, and very much fatter — was staring at him with great bulbous eyes. Suddenly it opened its mouth in a menacing yawn, and Franklin felt like Jonah at the big moment of his career. He had a glimpse of huge, blubbery lips enclosing surprisingly tiny teeth; then the great jaws snapped shut again and he could almost feel the rush of displaced water.
Don seemed delighted at the encounter, which had obviously brought back memories of his own days as a trainee here.
“Well, it’s nice to see old Slobberchops again! Isn’t he a beauty? Seven hundred and fifty pounds if he’s an ounce. We’ve been able to identify him on photos taken as far back as eighty years ago, and he wasn’t much smaller then. It’s a wonder he escaped the spear fishers before this area was made a reservation.”
“I should think,” said Franklin, “that it was a wonder the spear fishers escaped him.”
“Oh, he’s not really dangerous. Groupers only swallow things they can get down whole — those silly little teeth aren’t much good for biting. And a full-sized man would be a trifle too much for him. Give him another century for that.”
They left the giant grouper still patrolling the entrance to its cave, and continued on along the edge of the reef. For the next ten minutes they saw nothing of interest except a large ray, which was lying on the bottom and took off with an agitated flapping of its wings as soon as they approached. As it flew away into the distance, it seemed an uncannily accurate replica of the big delta-winged aircraft which had ruled the air for a short while, sixty or seventy years ago. It was strange, thought Franklin, how Nature had anticipated so many of man’s inventions — for example, the precise shape of the vehicle on which he was riding, and even the jet principle by which it was propelled.
“I’m going to circle right around the reef,” said Don. “It will take us about forty minutes to get home. Are you feeling O.K.?”
“I’m fine.”
“No ear trouble?”
“My left ear bothered me a bit at first, but it seems to have popped now.”