Not until the boys had changed to swimming trunks in the cabin of the _Water Witch_ did they find the answer to Zircon's question. The shadow had decided to stay with them. This time it was Rick who spotted him.

The shadow was nearly hidden beyond a curve in the sh.o.r.e line. To anyone not aware of being tailed, he would have appeared to be with any of the other casual figures that went unhurriedly about their business in the neighborhood. If Scotty hadn't pointed him out, Rick would not have suspected that the shadow had the slightest interest in the Spindrift party.

"We going to rig the aqualungs?" Scotty asked.

"Let's not bother. Masks, snorkels, and fins. We can swim out and take a look at some of the coral heads."

"How about a gun?"

Rick considered. "I guess not. We don't want to do any hunting. But you might take a hand spear in case something real inviting shows up. And let's take our knives." He had also decided against taking his camera. A leisurely, unenc.u.mbered swim was what he wanted. There would be time enough for hunting fish or taking pictures later, when they got to Clipper Cay.

While Scotty went into the cabin to select a spear from their a.s.sortment of fishing gear, Rick surveyed the _Water Witch_ with satisfaction. It was a thirty-five-foot craft with a small cabin forward and a s.p.a.cious c.o.c.kpit aft. It had been used as a diving tender before, apparently, because there was a ladder that could be swung outboard for a diver to use. There was also a small boom that could be rigged quickly for lowering or lifting gear from the water.

The gas tanks were ample for their purposes. One filling would be more than sufficient for a round trip to Clipper Cay plus any cruising they would do while at the island. The tanks were full.

Water capacity, an important consideration on waterless Clipper Cay, was more than adequate. In addition to a built-in fifty-gallon tank in the cabin, there was a rack of five ten-gallon jerry cans in the c.o.c.kpit.

Scotty emerged from the cabin with a short, low-powered spring gun.

"Thought I might as well bring a light gun," he said. "It's just as easy to carry as a spear."

"Okay." Rick led the way down the pier to the beach, carrying his mask, snorkel, and slippers. These he placed carefully on one of the Sky Wagon's pontoons, in order to protect the clear gla.s.s of his mask from any possible scratching. Then, with a yell to Scotty to hurry, he bounded through the shallows, threw himself forward, and planed along the surface of the water. Lifting his head for a quick breath, he dove under, feeling the wonderful coolness of the water close over him. He judged its temperature quickly. It was close to eighty degrees, he estimated, and cool only by comparison with the warm air.

He reversed course quickly and stood up. Scotty was also in the water.

"I'm glad we didn't bother with suits," Rick said. "In water like this we'd even be too warm in midseason suits."

Because of the coldness of the water off the New Jersey coast, the boys had equipped themselves with full, waterproof rubber suits under which long under-wear was worn, and with lighter "midseason" suits of foam neoprene. Because of the reported warmth of water in the Virgin Islands they hadn't added the suits to their already heavy load of supplies.

They returned to the beach, picked up their equipment, and took it into the water. Rick sat down and rinsed out his flippers, then carefully removed the last traces of sand from his feet. He pulled the flippers on, adjusting them for maximum comfort. His face mask was next. He spat into it, then rubbed the saliva over the gla.s.s. This rather unsanitary-appearing trick was essential, since saliva is an excellent antifogging compound needed to help keep the gla.s.s clear underwater.

Then he rinsed his mask lightly and adjusted the head straps, leaving the mask on his forehead.

The snorkels used by the boys were plastic tubes curved at both ends. At one end was a mouthpiece; at the other was a cage that held a rubber ball. A dive or rough wave action floated the ball upward, closing the tube and preventing water entry. Rick and Scotty adjusted the rubber bands of their snorkels around their heads above the mask straps.

Scotty was ready. He slipped his mask into place, molded the soft rubber skirt of the mask to the contours of his face, inhaled through his nose to make sure the seal was airtight, then called, "Let's go!" He gripped the mouthpiece of his snorkel between his teeth, the rubber f.l.a.n.g.e under his lips, and slid into the water.

Rick was right behind him. As his mask touched water he saw the white coral sand of the bottom a few inches down. The only sign of life was a hermit crab, perhaps a half inch in length, dragging his home of the moment--a tiny spiral sh.e.l.l.

In one hand, Scotty carried the spear gun by its pistol grip. He swam in the position that suited him best, both arms hanging limply down. Rick, on the other hand, preferred to swim with arms relaxed along his sides, as long as his hands were empty. When carrying a spear gun or his camera, he also swam with arms hanging downward. Neither boy used his arms for swimming. The rhythmic, powerful leg strokes were enough, thanks to the swim fins.

The water deepened rapidly but lost none of its clarity. Even at a depth of a dozen feet, Rick thought, he could have counted every grain of sand. This was unlike anything he had ever experienced. At home, visibility of five feet was considered good. Lost in the enjoyment of really clear water, he completely forgot about the shadow.

Scotty reminded him. He touched Rick's arm and signaled a stop. The boys removed their snorkel mouthpieces and faced each other upright in the water, holding position with easy flipper movements.

"Just pretend we're talking," Scotty said. "Don't look around. I'm trying to spot our friend over your shoulder." After a moment he shook his head. "No sign. Wonder if he ran for a bathing suit?"

"Forget him. Let's swim. See any coral heads?"

"Darker water off yonder. Let's look."

They readjusted their snorkels and headed in the direction Scotty had indicated.

Rick breathed easily through his tube, constantly scanning the bottom.

Now and then he saw various kinds of debris on the bottom, including abandoned beer cans and a section of newspaper that had not yet rotted away. Rubbish like this was to be expected in a harbor, he supposed, still it was as unattractive to a swimmer as junk along the roadside is to the motorist.

Suddenly he noticed a fish--the first he had seen. He took a deep breath and dove by letting his head drop and then lifting his legs to a nearly vertical position. He slid underwater without a splash. When his fins were below the surface he started his leg motion again, and the flippers propelled him smoothly downward.

The fish was perhaps a foot long, silvery, with a pointed nose and yellow fins. Rick couldn't identify it. The fish was busily rooting in the sand for morsels of food and paid no attention to the diver until Rick reached out and almost touched it, then it sped just beyond reach and commenced rooting again.

His curiosity satisfied for the moment, Rick surfaced and rejoined Scotty. As he took position at his friend's side, the other boy hooted once, their signal for "attention." The hooting was done by making a kind of "hooty" groan into the snorkel mouthpiece, about the only sound that could be made without letting water pa.s.s the lips. Because water conducted sound so well, the hoot could be heard clearly some distance away.

Rick lifted his face from the water and saw that Scotty was pointing to an area a short distance to their right. He followed Scotty's lead and saw the reason for the signal. It was a rocky, coral-covered area about thirty feet square and perhaps fifteen feet below the surface.

The boys swam directly over it, then floated motionless, watching the activity below. At first glance, there appeared to be only a pair of odd-shaped file-fish nibbling at the formation, but as their vision adjusted they made out literally dozens of tiny, colorful fish in clefts, under overhangs, or waiting motionless against a patch of color on the rocks. Rick pointed to a school of about ten vivid little fish of electric-blue color. The largest was less than two inches long. Scotty hooted for attention and pointed in his turn to a section of the rock that held over a dozen sea urchins that looked like black horse chestnuts with exaggerated spines.

Rick watched a pair of brown doctorfish about eight inches long swim by below, then his attention was attracted by a brilliant red squirrelfish peering out of a cleft. He pointed the red fish out to Scotty, who in turn showed him where a little moray was peering out of a hole near the base of the rock.

Rick was fascinated. If a tiny patch of rock held this amount of life, what must the real reefs be like off Clipper Cay? He was suddenly impatient to get going, to put on his aqualung and explore the reef from top to bottom. And if they should really find the wreck of the _Maiden Hand_, there was every chance that the exploration of the wreck and the sea life it had acquired would more than compensate for the treasure none of them really hoped to find anyway. What a vacation!

He was suddenly conscious of a throb in his ears. He listened and tried to identify it. A motorboat of some kind, but it didn't sound like a very powerful one. He lifted his head and searched for it.

Scotty, too, had heard the boat. He began to tread water, lifting his mask, then rinsing it because it had fogged a little.

Rick spotted the boat. It looked like a large row-boat, powered with an outboard motor, and it was headed in their direction.

Scotty took his snorkel out of his mouth. "Better stay topside and watch. We don't want to start our vacation by getting run over."

"Too true," Rick said. "Isn't this great? I've never seen so many kinds of small fish in one place in my life. Wait until we get out to the reefs where the big ones are."

Scotty patted his spear gun. "I'll keep us supplied with fresh sea food.

Wonder if there are any lobsters around?"

But Rick had stopped listening. "Scotty, that guy is heading right for us!"

The boat was getting close, and through his face plate Rick could make out the figure of a single occupant.

Scotty suddenly gripped his arm. "Rick! It's our shadow!"

Rick started. "Are you sure?"

"Yes. I don't like this. What would he come out here for? Get ready to dive." Scotty pulled his mask into place and molded it to his face, then gripped his snorkel between his teeth.

Rick followed suit and leveled off in the water in diving position, but he hesitated, waiting to see what the boat would do.

It didn't take long to find out. The boat stayed on a perfectly straight course, headed directly for them. Rick waited. Perhaps the shadow intended to sheer off when he got close. He might have come out to talk with them.

Scotty hooted four times, their signal for danger! Then he went under.

Still Rick hesitated, until it was clear that the boat did not intend to swerve. He saw the shadow's face, set in grim lines, then his legs went up and he slid under, using his hands as well as his legs to pull himself down to safety. He thought incredulously, "He tried to run us down!"

A dozen feet under he turned over on his back and saw the bright circle of the propeller and its trail of foam. The boat was past. He shot to the surface and filled his lungs with air, waiting for the next move.