The Air Chamber
Long Tian didn't rush back into the water. He sat on the deck for a while, wringing out his clothes and sleeves. Seawater flowed down the deck with his movements, soaking an area along the wood grain, shimmering continuously in the midday sun. Yu Jin handed him a dry biscuit, which he took, broke off a piece, and chewed, his gaze never leaving the sea ahead. The grayish-white line of water continued to float in front of the bow, its color lighter in the strong midday light, like the halo of light reflecting off a constantly polished stone surface, forming a persistent boundary line at the confluence of the flowing water and the light.
After finishing his dry biscuits, he took out the roll of fish skin paper from the cabin, unfolded it, and examined it again. The correspondence between the end of the dotted line and the underwater stone slab paving area highly overlapped with the direction of the diversion channel he had seen underwater, almost perfectly matching. He rolled the fish skin paper back up and put it in his leather bag, stood up, walked to the side of the boat, tightened the laces of his boots again in the sunlight, and then flipped over and went back into the water.
This time, he deliberately adjusted the angle of his descent. He sank along the edge of the light-colored waterline in front of the bow. After he entered the water, the Dragon Shadow rose from its back to its upper side, and the light layer on his forehead illuminated more of the underwater stone slab surface as it moved. The channeling grooves on the stone slab surface were denser than when he had seen them from the boat, with finer spacing and depth than the previous area. He swam forward along the direction of one of the channeling grooves. The channel turned a short distance ahead, pointing towards an area he hadn't observed closely before—a shallow concave surface appeared on the stone slab surface in this area, like a natural depression formed by water erosion. However, the rounded arc of the edge was too regular, not like a natural formation, but more like an arc surface formed by cutting and polishing.
He stopped at the edge of the concave surface. The concave surface was about two or three zhang in diameter and about half a person's height deep. Under the illumination of the lighting field, the stone at the bottom of the concave surface showed a different hue compared to the stone in other areas—a darker gray, with a smooth surface, unlike the state of being covered with sediment. Near the center of the bottom of the concave surface, there was a thin, elongated fissure, which ran in the same direction as the bow of the ship, about one and a half fingers wide, and its depth was not visible.
Long Tian swam around the edge of the fissure and stopped near the northern edge of the concave surface. He saw two rows of shallowly engraved symbols on each side of the fissure's edge, arranged symmetrically, as if intentionally carved as a set of comparative marks. The shapes of the symbols belonged to the same system as those on the walls of the mountain hall, but there were fewer symbols here, the arrangement was more regular, and the spacing was consistent. He did not try to interpret them, but simply noted down their arrangement and relative positions.
He floated back up along the inner wall of the concave surface, and when he reached near the edge, his fingers touched an area on the stone slab surface that differed from the surrounding texture—that area was smoother than the surrounding stone surface his fingertips touched, like a stone surface that had been polished for a long time. Its rectangular outline was about an arm's length long and half an arm's width, like a metal plate embedded in the ground that had been exposed to the constant alternation of air and water for a long time, forming a uniform oxide layer on its surface. He touched the edge of the rectangular area and felt an extremely fine gap at the edge, like the seam between a lid and the ground. He pushed along the seam with his fingertip, and the seam did not move, but he felt a very slight looseness—like a door that had been closed for a long time finally receiving a continuous response from the seam after a tentative push, like some long-frozen mechanical structure beginning to accept external force after a long period of inactivity, slowly adapting to the feeling of being pushed again.
He applied sustained pressure to the rectangular area with his palm. Under his continued pressure, the area began to slowly sink inward, like a device embedded in a base being pushed into its designed working position after a series of long-established structural linkages. The sinking process lasted for about three to five breaths, after which the area stopped at a fixed depth. As it stopped, it emitted an extremely low vibration, which traveled through the seawater to Long Tian's palm and arm, like a bell being struck below the surface, its fundamental tone spreading outward along the entire surface of the stone slab. As it traveled further through the water, it maintained a state of continuous attenuation but was not completely absorbed. In the distance, it gradually weakened due to continuous attenuation and diffusion, eventually disappearing into the deep sea background beyond sight.
Immediately afterward, Long Tian felt the surface of the stone slab beneath his feet slowly shift to both sides along the direction of the crack. As it shifted, the crack widened by about a palm's width, becoming an opening large enough for a person to pass through. A continuous flow of air—air—rushed out from within the opening. Bubbles surged from the opening, passing through the water layer, and burst into tiny water droplets above his head. The airflow carried a dry, warm scent, different from the surrounding seawater, like the residual warmth of a long-sealed space releasing the old air it had stored within.
As the opening widened, the Dragon Shadow descended to its edge. The light from its forehead shone down through the opening, illuminating an area devoid of water, containing only a short staircase and a section of dry stone floor. It resembled a long-standing space encased in a continuously waterproof structure, maintaining its dryness and air circulation due to its long period of stagnation. A section of stone steps extending downwards gleamed with a long-standing dim light under the Dragon Shadow's illumination, like a door that had been closed and never reopened, yet remained perpetually openable.