J ack swam to the edge of the tunnel and looked at the underwater magma lake, watching the yellow-brown haze that seemed to undulate over the lava as plumes of bubbles rose through it and shimmered towards the ceiling of the cavern in the darkness far above. He knew that to swim from the ledge over the lava would be like walking on quicksand, with the rising bubbles pulling on his buoyancy and the plumes acting like sinkholes in the water. Far out in the middle he watched a spectacular geyser of molten rock arch upwards, its surface speckled with bubbles of gas. He turned back, checking the gauge readout inside his helmet. They were eighty-five metres beneath the surface of the Black Sea, at least twenty-five metres below the outer flank of the volcano, and he was down to the final third of the air mixture in his rebreather. He had twenty-five minutes left at this depth, no more, before going on to his reserve supply. There would be no chance of an emergency ascent from this depth to the surface and Seaquest II; their only option was to stick to plan and return up the tunnel to the submersible. Getting to the ancient entranceway and then coming back here would be cutting it fine.
He turned to Costas, who had reached down and opened a Velcroed Kevlar flap on his left thigh, pulling out a tube about the length of his forearm. One end was attached to a spool of what looked like heavy-duty fishing line. He clipped the spool to a carabiner on the chest strap of his rebreather backpack and then twisted the tube, causing a handle like a pistol grip to fold out below. Another twist further up and a metal rod with a point like a harpoon snapped out of the front. He wrapped his right glove around the grip and put his other hand further up the tube. ‘I haven’t had a chance to show you this yet,’ he said.
‘Odd place to go spearfishing,’ Jack said.
‘It’s something I’ve been playing with since we were here five years ago,’ Costas replied, eyeing the rock face ahead of them. ‘You don’t tend to think that getting through submerged caverns would be an issue because you can swim through them, but thinking about volcanic activity made me wonder what it would be like if some force were dragging us down, exerting a pull on buoyancy exactly like those gas eruptions would do now.’
‘Got you,’ Jack exclaimed. ‘It’s a grapple gun.’
Costas pressed his wrist control panel, and Jack saw a thin shaft of light from his helmet where a laser rangefinder penetrated the gloom. ‘Twenty-six metres to that ledge,’ Costas murmured. ‘The grapple spear has a lead core to increase weight and the shaft is as narrow as possible for minimal water resistance, but even so its effective range is only about twelve metres. It’ll go further but you need good force of impact for the head to explode.’
‘Explode?’
‘The first ten centimetres of the shaft contains a joined matrix of rods made of titanium with a magnetic ferrous core. The head impacts the rock and detonates a small C-5 charge, and the rods shoot into every nook and cranny for ten centimetres or so around the point of impact. Then they’re locked tight by an electromagnetic pulse I fire down the wire from the gun.’
‘And then you reuse it?’ Jack pointed across the canyon. ‘We’re going to need two lengths.’
‘Once it’s wedged into the rock and magnetized, it won’t come out. But there’s a second head below the first on the shaft, and you can detach the line from the fired head and put it on the second. It’s a gamble, Jack. The total distance is several metres beyond the specs.’
‘How do we get back?’
‘That entranceway is about five metres higher than we are here. We’ll have to free-swim back, but if we launch ourselves with maximum buoyancy we could swim in an arc and land back here without being pulled down.’
‘Okay. Let’s get going.’
‘Move behind me. This thing fires a substantial black powder cartridge.’ Costas clicked on his laser rangefinder again and aimed at the jagged crevice he had been eyeing on the wall, then pulled the trigger. There was a violent shudder and a jet of bubbles and the spear shot off from the tube, pulling the line behind it. The spool abruptly stopped reeling and Costas was pulled forward, just holding himself in time from being yanked off the ledge over the rising bubbles. He pulled hard on the line, then looked back at Jack. ‘Okay. It’s held.’
‘What’s the drill?’
‘I stay here, you swim along the line. You get there, I swing off this ledge and follow you.’
Jack leaned over the void. ‘That line’s ten metres long, and the lava’s what, eight metres below us? That puts you in the soup.’
‘That’s where you come in. As I swim out as fast as I can from here, you reel in the slack. That way if I’m pulled down, the line will hold me high enough above the lava.’
‘Roger that,’ Jack said, pushing himself off and grasping the line in front of Costas. ‘You secure?’
‘Go for it.’
Jack finned forward over the lava, watching the streaks of red in the cooling lobes and nodules directly below him. At about the halfway point he was suddenly surrounded by a miasma of bubbles escaping from the lava below, a silvery mass that seemed to waft around him, bathing him in refracted light. He lost all points of reference, and seemed to be falling precipitately, a feeling that made him want to let go of the line and spread-eagle himself like a skydiver. His hand jerked on the line and he twisted sideways. It was no illusion; he really had been falling. He began pulling himself along, his buoyancy computer continuously adjusting to compensate for the effect of being dragged down in the vacuum created by the bubbles. He reached the grapple, checked that it was locked securely into a crack and then turned to look for Costas, who had crouched down on the edge of the tunnel opening, holding the line. Jack held on to the rock face with one hand and put his other out in the diver’s okay signal, his forefinger and thumb joined in a circle, and then transferred both hands to the line. He heard Costas’ voice crackling on the intercom through some kind of interference, the broken sounds briefly becoming distinct. ‘You ready?’
Jack wedged his body as much as he could into the rock. ‘Roger that.’
Costas launched himself forward in a slow-motion dive, his bulky suit making him look like an astronaut. As the line went slack, Jack hauled on it, looping it quickly around a rock protrusion behind him. It suddenly went taut as Costas was sucked down by a gas plume and disappeared out of sight. The line went slack again, and for a horrible few seconds as he frantically pulled on it Jack thought that Costas might have impacted with the lava. Then the crackling came on the intercom again, and Costas appeared out of the plume and ascended a few metres below him. He reached the ledge beside Jack, then wedged in an elbow and took the grapple gun out again from his pocket, unhooking the line from the carabiner on his chest and feeding it back into the tube. He glanced at Jack through his visor. ‘That was close.’
‘Your boiler suit looks like glue.’
Costas grunted, reached into the crevice to disengage the line from the grapple, then pressed a control on the tube to re-spool the line and hook it back into the second grapple, ready for firing. He wrapped his hand round the grip again and peered at their objective, the rock-cut platform in front of the ancient entranceway some fifteen metres away. ‘Twice lucky?’
‘Go for it.’
There was a jolt as he fired the device again, and Jack watched the grapple arc over and disappear into a fold in the rock about a metre below the ledge. Costas pulled hard, and the line went rigid. He leaned back and Jack swam over him, taking the line in one hand and kicking out above it. This time he quickly made it to the opposite side and Costas followed, swimming forward while Jack hauled, not bothering to loop the line but letting it drop down below. Costas reached the rock beside him and hung on, breathing heavily on his regulator, then he grasped the line near the grapple and let go of the rock to release the carabiner. As he did so, Jack saw a white expanse of gas billow up below them, and at the same moment the rock holding the grapple broke free under the tension and tumbled off the face, dropping down below Costas into the fomenting mass of bubbles now rising up around them. Jack wedged one hand into the rock and reached down with his other to grab Costas under one arm, holding tight as the plume rose through them. For a split second it seemed as if they were dangling in air, and Jack was holding Costas’ entire weight. Then the plume dispersed above them and Costas hit the manual on his buoyancy control. Jack twisted round and looked up, seeing the carved lintel shape above the doorway, straining to look for the ancient symbols he desperately wanted to see.
Just as he relaxed his hold, there was a jerk and Costas’ arm slipped away. Jack twisted back and saw a horrifying sight. Costas was at least five metres below him, his arms flailing, descending fast. Jack slammed his buoyancy control to dump the air inside his compensator and swam downwards. The chunk of rock with the grapple still inside had pulled Costas down like an anchor, and was now embedded in the lava near the edge of the chamber, sinking in and pulling Costas with it. Jack reached him with only a few metres to spare, pulling his chest
