‘The currents are strong here,’ Ishira informed them, ‘and the water contains a high volume of plankton and algae that can bring visibility down to less than five metres at times. Maintain close visual contact with each other and make sure you start your ascent with at least five minutes extra time available, because you’ll be fighting the currents to stay in position and will burn through your supply far quicker than during your descent.’
Both Ethan and Lucy nodded in agreement as they began pulling on their wetsuits, and Ishira hefted their oxygen tanks onto their backs and helped clip them into place.
The boat’s engine died down as Michael manoeuvred Jest into place directly overhead the flooded city, and moments later the clatter of a stainless steel chain rattled out across the rolling waves as he threw the anchor overboard. The anchor chain clattered through its stays and then slowed and pulled taut as the boat swung around into the current. Michael visually gauged the water passing the bow and then called out to them.
‘About four knots from the south-west,’ he reported. ‘It will be a little less down there but even so, I’d recommend using tethers just in case.’
Ethan shook his head. ‘If either one of us is pulled clear by the currents we’ll surface and let off a flare. It’s better for the boat to come after us then to be hindered by tethers when we need to move freely across the site.’
Michael shrugged but did not argue, although it was clear he felt that the waters were too choppy and the currents too strong to free dive the site.
‘Are you sure about that?’ Lucy asked him as they pulled on their flippers, Jest rocking and plunging on the swells.
‘We’ll start on the north-east corner of the site and then let the current move us down across it,’ Ethan informed her. ‘It’s sensible to let the current do the swimming for us. Once we’re done, we’ll ascend and have plenty of energy to maintain position.’
Lucy nodded her agreement. ‘Okay, but it’s a fairly big site so depending on the visibility we may have to split in order to see everything.’
‘And what exactly is it that we’re looking for? That icon in the photograph?’
‘Yes,’ Lucy replied. ‘Just keep an open mind and think about what you’ve learned so far. If there’s anything down there that could give us some pointers as to where we need to go, then pick it up or photograph it.’
Ethan pulled his oxygen mask on as he turned to sit on the edge of the boat with his back facing the water, Lucy moving alongside him. They checked each other’s oxygen supply and with a thumbs-up to each other Ethan held his mask in place as he went backwards over the edge of the boat. He only just heard Michael’s last comment before he plunged into the cold water.
‘Did I forget to mention the hammerhead sharks?’
The water flooded around Ethan’s body, and despite the highly effective thermal wetsuit he could feel the cold water on his hands and face. Ethan quickly orientated himself as he saw Lucy plunge into the water beside him amid a shimmering galaxy of bubbles, one hand over her mask as she reached back and tightened it in place and then gave him another thumbs-up.
Ethan looked around and saw that the water was presenting fairly good visibility, tinged with blue rather than the dull green that signalled a high organic content and reduced visibility. He looked down and was surprised to see that some ten feet beneath him was a perfectly flat surface of rock that extended away into the distance, marred only by clumps of mosses. It appeared to be made of sandstone, and almost instantly he spotted a perfect right angled corner to it just a few yards away.
For some reason he had expected to have to descend further to find the remarkable temple of which Lucy had spoken, but he could see already that it was nearby. He allowed his own natural weight to draw him down toward the surface of the monument as Lucy descended and moved to one side to hover over the edge.
Ethan swam to join her and looked down to see the side of the monument drop away onto a series of terraces, each of them cut at perfect right angles. Ethan had heard of numerous examples of natural phenomena creating such sharp right angles and angular features, most famously the Giant’s Causeway in Ireland. But here there was a difference: the monument itself stood alone and rose above the vast plain of the seabed. There was no evidence of erosion or loose rock that would have been evident had the effect of currents or similar been responsible for shaping the monument over geological timescales.
Ethan surveyed the overall shape of the monument. Despite the obvious geometric nature of the various structures that jutted from its surface, when Ethan swam away from the monument and looked at it as a whole it seemed clear to him that it was a natural formation that had later been modified by human hands. There seemed to be no plausible reason for human beings to have built such a large blocky construction, with no immediate obvious point of entry to any kind of interior. However, if they had instead been presented with a large feature such as the monument on a shoreline with an existing geometric shape that could be altered and upon which could be erected buildings, then it seemed likely that it would be used for as long as it was available to them.
Ethan looked across the surface of the monument and then considered the closeness of the shore of the island. His eye was drawn to the underside of the boat’s hull nearby, the water shimmering through the surface in bright beams. He looked again at the terraces on the right of the monument and suddenly he realized what he was looking at.
Ethan tapped Lucy shoulder and gestured to the boat before pointing at the terraces below them on the right of the monument. The terraces had always confused scientists who advocated the man-made nature of the site because the steps were too large for natural human movement and so had no apparent reason for being constructed or carved. But the monument had also been covered up by rapidly rising sea levels, and the terraces rose up in the direction of the nearby shore.
With a series of hand signals, Ethan indicated the lowest of the terraces near the front of the monument and pointed at the boat. Then he indicated the water around them, and raised his level hands in front of him up towards his head and over it and then pointed at the next level of terraces and the boat once more.
Lucy frowned for a moment and then her eyes widened as she realized what he was suggesting. The monument was not something built by human hands but modified as sea levels rose around it. The monument had been used as a dock, fresh terraces cut further and further away from the front of the monument as sea levels gradually rose in the wake of the Ice Age.
Suddenly, the so-called temples and altars made sense. They were not constructions in themselves, but features that had been carved smooth in order to build upon them: loading bays, steps, perhaps even a market where the so-called temple now stood. The altar may even have been a primitive sundial calendar, charting the passing of seasons for fishermen who might have lived and worked at this place. Only when the water became too deep and the level of the terraces reached the top of the monument was it finally overcome by the waves.
Lucy nodded, a look of delight in her eyes as she patted Ethan shoulder, clearly agreeing with his hypothesis of what the monument had actually been. Typically, in ancient civilizations, the presence of a natural harbour or a well-constructed dock had led to the establishment of major ports, from which major cities had then grown. The monument could easily represent all that remained of one of the oldest Japanese societies ever to have existed.
Ethan turned and saw that the monument extended some sixty yards long by perhaps forty wide and was at least eighteen yards deep. The terraces descended down on one side, while the temple beneath him extended down onto the surface of the main monument itself. Lucy produced in her hand a laminated map that she orientated to show the shape of the monument beneath him. Ethan could quickly identify the temple and the terraces, and also the shape of the angular altar to which Lucy pointed emphatically. Ethan nodded and turned to follow her as she began descending to where the altar should be.