We moved slowly forward, our fins stirring up fresh whirlpools of dirt and mud. Here also there were dead fish floating about us, although I noticed some of the red reef crayfish scrambling away like monstrous spiders into the depths of the ship. They at least had survived the blast in their armoured carapaces.

I played the beam of the torch on the deck above our heads, looking for the entry point to the lower decks and the holds. With the ship lying upside down, I had to keep trying to relate the existing geography of the wreck to the drawing I had studied. About fifteen feet from our entry point I found the forecastle ladder, another dark square opening above my head, and I rose into it, my bubbles blowing upwards in a silver shower and running like liquid mercury across the bulkheads and decking. The ladder was rotted so that it fell to pieces at my touch, the pieces hanging suspended in the water around my head as I went on into the lower deck.

This was a narrow and crowded alleyway, probably serving the pa.s.senger cabins and officers" mess. The claustrophobic atmosphere reminded me of the appalling conditions in which the crew of the frigate must have lived.

I ventured gingerly along this pa.s.sage, attracted powerfully to the doorways on either hand which promised all manner of fascinating discoveries. I resisted their temptation and finned on down the long deck until it ended abruptly against a heavy timber bulkhead.

This would be the outer wall of the well of the forward hold, where it pierced the deck and went down into the ship's belly.

Satisfied with what we had achieved, I turned the beam of the torch on to my wrist and realized with a guilty thrill that we had overrun our working time by four minutes. Every second was taking us closer to the dreaded danger of empty air bottles and uncompleted decompression stops.

I grabbed Sherry's wrist and gave her the cut-throat hand signal for danger before tapping my wrist.w.a.tch. She under, stood immediately, and followed me meekly on the long slow journey back through the hull along the guiding line. Already I could feel the stiffening of the demand valve as it gave me air more reluctantly now that the bottles were almost exhausted.

We came out into the open and I made certain that Sherry was by my side before I looked upwards. What I saw above me made my breathing choke in my throat, and the horror I felt turned to a warm oily liquid sensation in my bowels.

The pool of Gunfire Break had been transformed into a b.l.o.o.d.y arena. Attracted by the tons of dead fish that had been killed by the blast, the deep-water killer sharks had arrived in their scores. The scent of flesh and blood, together with the excited movements of their fellows transmitted to them through the water, had driven them into that mindless savagery known as the feeding frenzy.

Quickly I drew Sherry back into the gunport and we cowered there, looking up at the huge gliding shapes so clearly silhouetted against the light source of the surface.

Amongst the shoals of smaller sharks there were at least two dozen of the ugly beasts that the islanders called Albacore shark. They were barrel-bodied and swing-bellied, big powerful fish with rounded snouts and wide grinning jaws. They swirled about the pool like some grotesque carousel, with their tails waggling and their mouths opening mechanically to gulp down shreds of flesh. I knew them for greedy but stupid animals, easily discouraged by any aggressive display when not in feeding frenzy. Now they were in intense excitation they would be dangerous, yet I would have accepted the risk of a decompression ascent if it had been for them alone.

What truly appalled me were two other long lithe shapes that sped silently about the pool, turning with a single powerful flick of the long swallow tail, so that the pointed nose almost touched the tip of the tail, then gliding away again with all the power and grace of an eagle in flight.

When either one of these terrible fish paused to feed, the sickle-moon mouth opened and the multiple rows of teeth came erect like the quills of a porcupine and flared outwards.

They were a matched pair, each about twelve feet in length from nose to tail-tip, with the standing blade of the dorsal fin as long as a man's arm; they were slaty blue across the back and with snowy white bellies and dark tips to tail and fins, they could bite a man in half and swallow the pieces whole.

One of them saw us crouching in the mouth of the gunport, and it turned sharply and came down over us, planing a few feet above us as we cowered back into the gloom so that I could clearly see the long trailing spikes of the male reproductive organs.

These were the dreaded white death sharks, the most vicious fish of all the seas, and I knew that to attempt to ascend in the clear and decompress adequately with limited air and no protection would be certain death.

If I were to get Sherry out alive I would have to take risks that in any other circ.u.mstances would be unthinkable.

Quickly I scribbled on the slate: "STAy! I am free ascending for air and gun."

She read the message and immediately shook her head in refusal and made urgent signs to prevent me, but already I had pulled the pin out of the quick release buckle of my harness and I took the Last deep, chest-swelling breath before I thrust my scuba set into her hands. I dropped my weight belt to give myself buoyancy and slid down the side of the hull, using the wreck to cover me as I finned swiftly for the cover of the cliff.

I had left Sherry what remained of my air supplies, perhaps five or six minutes" breathing if she used it sparingly, and now with only the air that I held in my lungs I had to run the gauntlet of the pool and try for the surface.

I reached the cliff and began to go up, close in against the coral, hoping that my dark suit would blend with the shades. I went up with my back to the coral, facing out into the open pool where the great sinister shapes still swirled and milled.

Twenty feet from the bottom and the air in my lungs was expanding rapidly as the pressure of water decreased. I could not hold it in or it would rupture the tissue of my lungs. I let it trickle from my lips, a silver beacon of bubbles that one of the white death sharks noticed immediately.

He rolled and turned, dashing across the pool with slashing strokes of his tail, bearing down upon me. Desperately I glanced up the cliff and found six feet above me one of the small caves in the rotten coral. I dived into it just as the shark flashed past me, turned and sped back for a second pa.s.s as I shrank into my shallow shelter. The shark lost interest and swirled away to pick up the falling-leaf body of a dead snapper, gulping it down convulsively.

My lungs were throbbing and pumping now for the oxygen had all been absorbed from the air I held, and the carbon dioxide was building up in my blood. Soon I would begin to black out into anoxia.

I left the shelter of the cave, but, still following the cliff, I drove upwards as hard as I could with the single swimming fin, wishing bitterly for the use of the other still trapped under the gun carriage.

Again I had to release expanding air as I rose, and I knew that in my veins nitrogen was also decompressing too rapidly and soon it would turn to gas and bubble like champagne in my blood.

Above "me I saw the silvery moving mirror of the surface and the black cigar shape of the whaleboats hull suspended upon it. I was coming up fast and I glanced down again. Far below me I could see the shark pack still milling and turning. It looked as though I had escaped their notice.

My lungs burned with the craving for air, and the blood pounded in my temples as I decided that the time had arrived when I must forsake the shelter of the cliff and cross the open pool to the whaleboat.

I kicked out and shot towards the whaleboat where it lay a hundred feet from the reef. Halfway across I glanced down and saw one of the white deaths had seen me and was chasing. It came up from the blue depths with incredible speed, and terror gave me new strength as I drove for the surface and the boat.

I was looking down, watching the shark come. It seemed to swell up in size as it rushed towards me. Every detail was burned into my mind in those frantic seconds. I saw the hog's snout with the two slitted nostrils, the golden eyes with the black pupils like arrowheads, the broad blue back from which stood the tall executioner's blade of the dorsal fin.

I came out through the surface so fast that I broke clear to my waist, and I turned in the air and got my good arm over the gunwale of the boat. With all my strength I swung my body forward and jack-knifed my legs up under my chin.

In that instant the white death struck, the water exploded about me as he burst through the surface, I felt the harsh gritty skin tear across the legs of my suit as he brushed against me, then there was a shuddering crash as he struck the hull of the whaleboat.

I saw Chubby and Angelo's startled faces as the boat heeled over and rocked wildly. My violent contortions had thrown the shark off his run, and he had missed my legs and collided with the hull.

Now with one more desperate kick and heave I tumbled over the gunwale and fell into the bottom of the whaleboat. Again the shark crashed into the hull as I went over, missing me again by inches.

I lay there pumping air into my aching lungs, great sweet gulps of it that made me light-headed and giddy as on strong wine.

Chubby was yelling at me, "Where is Miss. Sherry? That big Johnny Uptail get Miss. Sherry?"

I rolled on to my back, panting and sobbing for the precious air.

"Spare lungs," I gasped. "Sherry waiting in the wreck. She needs air."

Chubby leaped into the bows and dragged the canvas sheet off the extra scuba sets stacked there. In a crisis he is the kind of man I like to have covering for me.

"Angelo," he growled, "get them Johnny pills." They were a pack of copper acetate shark repellent pills which I had ordered from an American sports goods catalogue and for which Chubby had professed a deep and abiding scorn. "Let's see if those fancy things are any b.l.o.o.d.y good."

I had breathed enough to drag myself off the floorboards and to tell Chubby: "We've got problems. The pool is full of big Johnnys, and there are two really mean uptails with them. That one that charged me and another."

Chubby scowled as he fitted the demand valves to the new sets.

"Did you come straight up, Harry? I nodded. "I left my bottles for Sherry. She's waiting down there."

"You going to bend, Harry?" He looked up at me and I saw the worry in his eyes.

"Yes," I nodded, as I dragged myself to my tackle box and lifted the lid. "I've got to get down again fast - got to put pressure on my blood again before she rises."

I picked out the bandolier of explosive heads for my hand spear.

There were twelve of them, and I wished for more as I strapped the bandolier around my thigh. Each head was hand-tapped to screw on to the shaft of a ten-foot stainless steel spear. It contained explosive charge equivalent to that of a 12-gauge shotgun sh.e.l.l and I could fire the charge with a trigger on the handle. It was an effective shark-killer.

Chubby hoisted one of the scuba sets on to my back and clinched the harness, and Angelo knelt before me to strap the shark repellent tablets in their perforated plastic containers to my ankles.

"I'll need another weight belt," I said, "and I lost a fin. There is a spare set in, I did not finish the sentence. Blinding burning agony struck me in the elbow of my bad arm. Agony so fierce that I cried aloud, and my arm snapped closed like the blade of a clasp knife. It was an involuntary reaction, the joint doubling as the pressure of bubbles in the blood pressed on nerve and tendons.

"He's bending," snarled Chubby. "Sweet Mary, he's bending." He leapt to the motors and gunned them, taking me in close to the reef. "Work fast, Angelo," Chubby shouted, we got to get him down again."

The pain struck again, a fiery cramping agony in my right leg.

The knee doubled under me and I whimpered like an infant. Angelo strapped the weight belt around my waist, and thrust the swimming fin on to my crippled leg.

Chubby cut the motors and we coasted in under the lee of the reef, while Chubby scrambled back to where I crouched on the thwart. He stooped over me to thrust the mouthpiece between my lips and open the c.o.c.ks on the air bottles.

"Okay?" he asked, and I sucked from the set and nodded. Chubby leaned over the side and peered down into the pool. "Okay," he grunted, "Johnny Uptail gone somewhere else."

He lifted me like a child, for I had lost the use of arm and leg, and he lowered me into the water between boat and reef.

Angelo hooked the harness of the extra scuba set for Sherry on to my belt, then he pa.s.sed me the ten-foot spear and I prayed that I would not drop it.

"You go get Miss. Sherry out of there," said Chubby, and I rolled over in a clumsy one-legged duck dive and went down.

Even in the cramping agony of the bends my first concern was to search for the sinister gliding shapes of the white deaths. I saw one of them, but he was deep down, amongst the pack of lumbering Albacore sharks. Cliriging to the shelter of the reef, I kicked and wriggled downwards like a maimed water beetle. Thirty feet under the surface the pain began to recede. Renewed pressure of water was reducing the size of the bubbles in my bloodstream, MY limbs straightened and I had use of them.

I went down faster, and the relief was swift and blessed. I felt new courage and confidence flooding away my earlier despair. I had air and a weapon. I had a fighting chance now.

I was ninety feet down, in clear sight of the bottom. I could see Sherry's bubbles rising from the smoky blue depths, and the sight cheered me. She was still breathing, and I had a fully charged extra scuba set for her. All I had to do was get it to her.

One of the fat ugly Albacore sharks saw me as I slid down the dark cliff face, and he swerved towards me. Already gorged with food, but endlessly hungry, he came in at me grinning horribly and paddling his wide tail.

I backed up and hung in the water against the cliff, -facing him.

I had the spear with its explosive head extended towards him, and as I finned gently to hold myself ready the streamers of bright blue dye from the shark repellent tablets smoked out in a cloud around me.

The shark came on in, and I lined up to hit him fairly on the snout, but the instant his head and gills encountered clouds of blue dye he spun away, flapping his tail in shock and dismay. The copper acetate had burned his gills and eyes, and he retreated hurriedly.

"Eat your liver, Chubby Andrews," I thought. "They work!" Down again I went, almost to the tops of the bamboo finest, seeing Sherry still crouched in the gunport thirty feet away watching me. She had exhausted her own air bottles and was using mine - but I could tell by the volume and scanty rate of flow of bubbles that she had only seconds of breathing time left to her.

, I started towards her, leaving the cliff - and only her frantic hand signals alerted me. I turned and saw the white death coming like a long blue torpedo" He was skimming the tops of the bamboo, and from one corner of his jaws hung a tattered streamer of flesh. He opened that wide maw to gulp, down the morsel, and the rows of fangs gleamed whitely, like the petals of some obscene flower.

I faced him as he charged, but at the same time I fell back kicking my fins in his direction and laying a thick smoke-screen of blue dye between us.

With hard slashing strokes of his tail, he arrowed in the last few yards, but then he hit the blue dye and swirled, altering the direction of his charge as he sheered away.

He pa.s.sed me so close that his tail struck me a heavy blow on the shoulder, sending me tumbling end over end. For seconds I lost my bearings, but as I recovered my balance and looked wildly about me I found the great shark circling.

He swept around me, forty feet away, and in his full length he seemed to my heated eye as long as a battleship and as blue and as vast as a summer sky. It seemed impossible to believe that these fish grew to almost twice this size. This one was still a baby - I was thankful for that.

Suddenly the slim steel spear in which I had placed so much faith seemed futile, and the shark regarded me with a cold yellow eye across which the pale nict.i.tating membrane flicked occasionally in a sardonic wink, and once he opened his jaws in a convulsive gulp, as though in antic.i.p.ation of the taste of my flesh.

He continued in those wide racing circles, with myself always at the centre, turning with him and paddling frantically with my fins to match his smooth unforced speedas I turned, I unhooked the spare lung from my back and slung it by the harness on my left shoulder like the shield of a Roman legionary, and I tucked the hilt of the spear under my arm and kept the head pointed at the circling monster.

My whole body tingled with the warm flush of adrenalin in the bloodstream, and my senses were enhanced and sharpened by the adrenalin high - the intensely pleasurable sensation of acute fear to which a man can become an addict.

Each detail of the deadly fish was etched indelibly on my memory, from the gentle pulsing of the multiple gill behind the head to the long trailing ribbons of the remora fish holding by their suckers to the smooth snowy expanse of his belly. With a fish of this size, it would only infuriate him further if I went for a hit with the explosive spear on his snout. My only chance was for a hit on the brain.

I recognized the moment when the shark's distaste for the blue mist of repellent was overcome by his hunger and his anger. His tail seemed to stiffen and it gave a series of rapid strokes, driving his speed up sharply.

I braced myself, lifting the spare scuba protectively, and the shark turned hard and fast, breaking the wide circle and coming in directly at me.

I saw the jaws open like a pit, lined with the wedgeshaped fangs, and at the moment of strike I dintst the twin steel bottles of the scuba into it.

The shark closed its jaws on the decoy and it was torn from my grasp, while the impact of the attack tossed me aside like a floating leaf. When I had gathered myself again I looked around ftantically and found the white death was twenty feet away, moving only slowly but worrying the steel bottles the way a puppy chews a slipper.

It was shaking its head in the instinctive reaction which tears lumps of flesh from a victim - but which was now inflicting only deep scratches on the painted metal of the scuba.

This was my chance, my one and only chance. Kicking hard, I spurted above the broad blue back, brushing the tall dorsal fin and I sank down over him, coming in on his blind spot like an attacking fighter pilot from high astern.

I reached out with the steel spear and pressed the tip of it firmly on to the curved blue skull, directly between those cold and deadly yellow eyes - and I squeezed the springloaded trigger on the hilt of the spear.

The shot fired with a crack that beat in upon my eardrums, and the spear jumped heavily in my grip.

The white death shark reared on its tail like a startled horse, and once again I was. tossed lightly aside by his careless bulk, but I recovered to watch him go into a terrible frenzy. The muscles beneath the smooth skin twitched and rippled at random impulse from the damaged brain, and the shark spun and dived, rolling wildly on its back, arrowing downwards to crash snout first into the rocky bottom of the pool, then it stood on its tail and scooted in aimless parabolas through the pale blue waters.

Still watching it, and keeping a respecthil distance, I unscrewed the exploded head off the spear and replaced it with a fresh charge.

The white death still had Sherry's air supply clamped in his jaws.

I could not leave it. I trailed his violent, unpredictable manoeuvres warily, and when at last he hung stationary for a moment nose down, suspended on the wide flukes of his tail, I shot in again and once more pressed the explosive charge to his skull, holding it firmly against the cartilaginous dome, so that the full shock of the charge would be transmitted directly to the tiny brain.

I fired the shot, cracking painfully in my own ears, and the shark froze rigidly. It never moved again but still in that frozen rigour it rolled over slowly and began to sink towards the floor of the pool. I darted in and wrested the damaged scuba from his jaws.

I saw immediately the air hoses had been torn and shredded by the shark's teeth, but the bottles were only extensively scratched.

Carrying the lung with me I sprinted across the tops of the bamboo towards the wreck. There were no longer air bubbles rising from the gunport, and as I came in sight of her I saw that Sherry had discarded the last empty scuba set. They were empty, and she was dying slowly.

Yet even in the extremes of slow suffocation she had not made the suicidal attempt to rise to the surface. She was waiting for me, dying slowly, but trusting me.

As I came down beside her, I pulled out my own mouthpiece and offered it to. her. Her movements were slow and uncoordinated. The mouthpiece slipped from her grasp and floated upwards, spewing out a torrent of air. I grabbed it and forced it into her mouth, holding it there while lowering myself slightly below her level to induce a readier flow of air.

She began to breathe. Her chest rose and fell in long deep draughts of the precious stuff, and almost immediately I saw her regaining strength and purpose. Satisfied I turned my attention to removing a demand valve from one of the abandoned lungs from which the air supply was exhausted and using it to replace the one damaged by the shark.

I breathed off it for half a minute, before strapping it on to Sherry's back and retrieving my own mouthpiece.

We had air now, enough to take us through the long period of slow decompression ahead of us. I knelt facing Sherry in the gunport and she grinned lopsidedly around the mouthpiece and lifted her thumb in a high sign and I returned it. You okay, me okay, I thought, and unscrewed the expended head from the spear and renewed it from the bandolier on my thigh.

Then once more I peered from the safety of the gunport out into the open waters of the pool.

As the supply of dead. fish was depleted so the shark pack seemed to have dispersed. I saw one or two of the ungainly dark shapes still searching and sniffing the tainted waters, but their frenzy was reduced. They moved in a more leisurely fashion, and I felt happier about taking Sherry out now.

I reached for her hand and was surprised at how small and cold it felt in mine, but she answered my gesture with a squeeze of her fingers.

I pointed to the surface and she nodded. I led her out of the gunport and we slid down the hull and under cover of the bamboo crossed quickly to the shelter of the reef.

Side by side, still holding hands and with our backs to the cliff, we rose slowly up out of the pool.

The light strengthened and when I looked up I could see the whaleboat high above. My spirits rose.