Wall Shadow
The boat traveled for nearly three hours after nightfall.
There was no moon on the sea; the clouds hung low, pressing the starlight into a thin, even gray light that spread across the water. The person at the stern fell silent, one hand on the rudder, occasionally adjusting it slightly according to the direction the Dragon Shadow at the bow was tilting its head. The Dragon Shadow maintained a stable posture as it continued to sail, its two heads tilting at different angles—the left head tilted to the northwest, as if sensing some kind of lateral flow; the right head extended to the southeast, the light layer at the edge of its wing membrane spreading into a thin band of light in the moonless night, extending along the surface of the water.
Yu Jin squatted by the ship's side, dipping his hand into the water. Every now and then, he would pull his hand back to look at the residue on his fingertips before putting it back in the water. Long Tian sat at the bow, his gaze fixed on the sea ahead, watching the color of the water change from deep blue to a thicker inky black as the voyage continued, like a base color that had been repeatedly blurred and deepened until it finally reached its final saturation.
About half an hour later, the boat suddenly slowed down. The man at the stern pushed the rudder half an inch to the left, and the boat came to a smooth stop at an unseen boundary. He crouched down and took a long rope from the cabin, tying one end to an iron ring at the bow and the other end to an old iron weight, then lowered the weight into the Long Tian, saying, "We're here. The top of that wall is at this depth. The weight slid over an angled surface; the wall on our side is sloping, not vertical."
Long Tian stood up and walked to the side of the boat, holding onto the railing as he looked down. About two zhang below the surface, there was a darker outline than the surrounding seawater, like a dark sheet pressed beneath a transparent layer. Dragon Shadow descended from above the bow to the water's surface, a sliver of light seeping from the vertical line on his forehead, piercing through the water and illuminating the surface of the dark outline—it was the top of a flat stone wall, covered with a thin layer of sediment. However, the sediment was unevenly distributed, revealing the stone's original color in the areas where the light swept across it: a deep gray, almost black, hue, like the surface of an iron plate that had been repeatedly quenched.
Long Tian took off his coat, folded it neatly, and placed it on a dry spot by the ship's side. He tightened the straps of his leather pouch. Yu Jin stepped back from the ship's side, making way for him. The person at the stern remained silent, retrieving the iron weight's rope back into the cabin. Long Tian stood by the ship's side for a moment, the two heads of the Dragon Shadow behind him lowering slightly, like two flags simultaneously lowered by the same gust of wind. He took a deep breath, stepped onto the edge of the ship, and flipped into the water.
The impact of the temperature difference upon entering the water was more pronounced than he had anticipated. A clear transition layer existed between the surface seawater and the bottom, like passing through a curtain separated by air of different temperatures. After sinking into that transition layer, he sensed the underwater current—different from the direction at the surface, it was continuously moving southeast, at a slow but steady pace, like a conveyor belt fixed in the depths. He adjusted his posture, and the Dragon Shadow reattached itself to his back after he entered the water. The wing membranes folded into narrow strips suitable for underwater movement, and the direction of light propagation in the seawater changed from direct light in the air to scattering, spreading around him and forming an illumination field about ten feet in diameter.
Under the illumination, Long Tian could see the entire wall. It was a wide stone structure with a flat top, rising about two zhang (approximately 6.6 meters) from the bottom of the water before reaching its top. The two sides extended into the distance, continuing to stretch beyond the range of light. The stone bricks of the wall were of uniform size, with tight joints, and the surface had evenly arranged shallow longitudinal grooves, like drainage channels. He swam along the edge of the top of the wall for a while. After extending for about ten zhang, the wall bends outward at an almost right angle. The masonry technique at the bend is the same as that of the main body, and there are no cracks at the structural joints, as if it were built as a single piece.
He stopped at the bend and pressed his hand against the surface of the top of the wall. The sediment crumbled under his pressure, revealing the stone beneath. The stone didn't have the rough, granular feel of ordinary stone; instead, it had a denser, smoother texture, as if it had been polished by flowing water for a long time and then covered with a thin layer of crystals. The edge of the wall continued southeast after the bend, narrowing into a gap about half a foot wide at the end of the light-filled area, like a door that had been left open but wasn't fully opened.
Long Tian floated above the crevice, looking down. The space inside the crevice was deeper than the outer wall, as if the wall had stopped here and then started again. He sank a little deeper along the edge of the crevice, and when he was close to the foundation of the wall, he saw the ground at the bottom of the crevice—paved with stone slabs, the same material as the wall, with no sediment on the surface, as if it had been washed extremely clean by water. Several parallel lines were carved on the stone slabs, regularly spaced, and in the same direction as the wall.
He surfaced for a breath, then clung to the edge of the gunwale and climbed back onto the boat. Water dripped from his clothes and hair onto the deck, pooling at his feet. After he returned, the Dragon Shadow rose again from its back to above the gunwale, its wing membranes unfurling in the air, shedding a fine layer of water droplets, like a flag pulled from the water and unfurled by the wind. He crouched by the gunwale, wiping the water from his face, and turned to the man at the stern, saying, "There's a door in that wall down there. The crack wasn't opened; it was left open. Like a door waiting for a perfectly fitting key to turn." As he spoke, water droplets continued to drip from his chin, making a soft, muffled sound on the deck, like a diminished raindrop drowning out the lingering echoes of waves lapping against the gunwale.