In the seconds it took him to leave the deck, his mind had flashed through the physiology of free diving: the possibility of middle ear and sinus rupture if he failed to equalize, and the inevitability of lung barotrauma and blood shift into the capillaries as his chest cavity was squeezed. Yet there was also the reflexive response of the body to being underwater, the reduction of metabolic rate that could allow him to remain conscious for the crucial few extra seconds he might need to reach the submersible and open the air-tank manifold to give Costas a chance of survival.
Below him lay almost a thousand meters of water to the wreck of the Beatrice. At that depth without a pressure suit, his organs would be crushed, but he would have been dead a long time before that. With every ten meters of depth from the surface, his lungs would halve in volume, so that at fifty meters the air that had filled his lungs would occupy only one-fifth of that volume, at a hundred meters one-tenth. By a hundred and fifty meters, lung barotrauma was a near certainty. The constricting volume of his chest cavity would cause the membranes to rupture, and he would begin to drown in his own blood. By then, perhaps two minutes or two and a half minutes into the dive, he would be reaching the limit of his breath-holding endurance. At that point he would either give way and breathe in water, or black out because the increased carbon dioxide level in his body would trigger unconsciousness. Either way meant death. All he knew for certain was that the maximum free-diving depth ever achieved had been a little over 250 meters, less than a quarter of the depth of the water below him now and representing almost superhuman physiological endurance. If the submersible had dropped any deeper than that before he reached it, there could be only one possible outcome, for him as well as for Costas.
He was instinctively prepared for a shock of cold, but as he sliced into the water he felt the warmth of the Mediterranean envelop him. He knew that the cold would come, a rapid, numbing cold as he passed through the thermocline, and that the oxygen saturation in his brain was inducing a mild sense of euphoria, something that would wear off quickly as the oxygen was depleted. As he felt himself plummet, he concentrated on equalizing his ears, his eyes shut tight. To open them in the pellucid water would be to reveal the enormity of the darkness beneath him, something that would make even the strongest diver balk. He would do so only once he had passed the point of no return, once he knew that bailout was impossible.
Less than ten seconds after entering the water, he passed the first big thermocline, at this time of year at a depth of about thirty-five meters. Even if he dropped the weights, he knew that without fins he would stand no chance of returning to the surface now. The cold increased his sense of speed, his skin more sensitized to the water rushing past. Equalizing became easier as the pressure differential decreased, each halving of the air spaces in his body every ten meters now involving smaller and smaller volumes of gas. He was deeper than he had ever free-dived before — eighty, perhaps ninety meters — far beyond the safe depth for compressed-air diving, well into the death zone, where the chances of sudden unconsciousness increased dramatically with every meter of descent.
He felt a searing pain in his lungs, as if a clamp were compressing his chest from all sides, tightening with every second that passed. Even if there had been air to breathe, he felt that his chest could never bear the expansion. The cold was shocking now, as cold as the Arctic Ocean, further paralyzing him. He knew he had little time, maybe half a minute, no more. He opened his eyes. For a few seconds he was distracted from the agony in his body as he concentrated on trying to see. He looked down, blinking against the blur. Directly below him it was pitch dark, an absolute darkness like he had never seen before. He had the sense that he was sinking into it, that he had plummeted below the final gloom of natural light. He knew that meant he was at least 120 meters deep, probably closer to 150 meters. For an instant the pain seemed to leave him and he felt himself holding Rebecca tight, a memory of a moment when he had felt that his life had been most worthwhile, a moment of utter contentment. He forced himself out of it, back to reality. He needed to remain focused for his final seconds, even if it meant excruciating pain. Costas.
And then he saw it. A few meters below him, a suffused glow appeared, the emergency lighting of the submersible. He hit the cable and slid down it, the metal cutting into his exposed forearm. He crashed into the carapace of the submersible like an astronaut out of control on a spacewalk. He let go of the weight belt, which spun a crazy dance into the depths, disappearing out of sight below. He saw the recumbent form of Costas watching him through the viewing port of the bathysphere, his face distorted by the thick Perspex. He pulled himself over to the manifold linking the air cylinders together and found the wheel that opened the valve, seeing where it had been bent over by the cable falling on it. He pulled it anticlockwise. Nothing. He tried again, using every fiber of his being, every ounce of energy he had left. Still nothing. He suddenly felt the overwhelming urge to breathe, and began gagging, each reflex sending a jolt of pain through his lungs. He caught sight again of the face in the porthole. He could not give up now. He heaved one last time, and suddenly it gave way, cracking open. He spun the wheel around several times and pulled himself frantically down to the wheel that opened the double-lock chamber, spinning that too, feeling the hatch open inward and pulling himself inside, pushing it shut and slamming his hand down on the handle that opened the valve to fill it with air.
A deafening hiss filled his ears, and the water in the chamber became a raging maelstrom, lit up by the orange glow of the emergency lighting. Seconds later his head was above water, and he was gasping, taking in huge lungfuls of air, shuddering as the oxygen coursed through him. He coughed hard and saw a fine mist of red, evidence of some respiratory tissue damage but not enough to indicate major barotrauma. He saw blood drip from his nose, and he tipped his head up. He glanced at his watch; it had been a little over four minutes since he had last looked at it on the deck of the ship just before jumping. The depth gauge on the casing of the chamber showed 275 meters, and was increasing rapidly. In the course of tangling with the submersible, he had dropped through the threshold of possibility for free diving. Another ten meters and he would probably have been gone. He had been lucky.
The chamber emptied of water, the hissing stopped, and the hatch from the bathysphere clanged open. Costas’ head appeared through it. “Jack. Good of you to drop in.”
Jack coughed again, his voice hoarse, distant sounding. “Don’t mention it.”
“You okay?”
Jack tipped forward, a finger pressed against his nose. “Could use a tissue.”
Costas fumbled in the pocket of his overalls, leaned in, and passed over a scrunched ball of white. Jack took it, holding it cautiously. “Pre-used?”
“Tried and tested.”
Jack wet it, tore off a chunk, shoved it up his nostril, and held it there. He cautiously tipped forward again and saw that the bleeding had been stemmed. His breathing had nearly returned to normal, and he edged forward, noticing for the first time the gash like a deep rope burn on his left forearm where he had slid down the cable. Costas handed him a towel, a fleece, and a pair of tracksuit bottoms. “My spare clothes. A little short and a little wide, but who’s looking. Once we get into the bathysphere, we’ll dig out the first-aid kit for that arm.”