The Tide Line
The ship arrived at the area the old man had described on the afternoon of the third day.
The color of the seawater gradually changed from the yellowish-green near the shore to the deep blue of the open sea. Then, an uneven transition layer appeared on the outer edge of that area—like two streams of different colors converging here, not completely merging, but simply occupying their own sections of water side by side, forming a continuous wave line at the boundary. Long Tian stood at the bow of the ship and looked in the direction of that wave line. At this moment, the Dragon Shadow above his shoulder and back followed the same direction as the color difference line on the sea surface, like a slender object that had been stirred by the wind and found a stable position again.
Yu Jin crouched at the stern, dipped one hand into the water for a moment, and when he withdrew his hand, his palm was still warm, cooler than the surrounding seawater. The luster of the dark gray bead on his collarbone shone brighter than on land above the sea, like a fully moistened Shitou maintaining its even luminosity in the continuous dampness. He shook the water droplets off his hand and placed it back on the gunwale.
As the boat continued forward, the seawater ahead began to shallow—not in depth, but in color, changing from deep blue to a grayish-blue-green, like a thin filter covering the surface. Occasionally, the keel scraped against an unknown shallow ridge, the hull emitting a low, grinding sound, but it didn't stop. Long Tian probed the depth with his oar; the tip stopped at a hard surface, like touching some hard plane covered by years of water flow on the earth's surface. He pulled the oar back, water dripping from the edge of the blade, leaving a dark, damp ring on the wooden planks of the hull.
As he retracted the oars, the Dragon Shadow rose from its back, hovering about two zhang (approximately 6.6 meters) above the water's surface in front of the bow. Its wings were slightly spread, and its four eyes continued to gaze downwards. At that moment, a very thin ray of light pierced through the vertical line on its forehead, penetrating the surface of the seawater and forming a visible spot of light on the hard plane below. The spot of light moved slightly about one zhang (approximately 3.3 meters) below the surface, extending forward along a horizontal line, as if scanning the structural outline beneath the surface.
Long Tian rowed forward along the direction of the light spot. The light spot stopped at a point where the water was a darker shade, and then its brightness gradually increased, like a lamp being turned on. He put down the oar, leaned over the bow, and dipped his hand into the water. The water was colder than expected and flowed faster, as if someone was constantly pulling the current from below. When his fingers touched the layer of water below the light spot, he felt a force pushing against the current from the bottom. He withdrew his hand, his fingertips covered with a layer of grayish-white dust—the same texture as the powder on the platform of the mountain hall, only finer, and in contact with the water, it was in a state between dissolving and suspending.
Yu Jin walked from the stern to the bow, squatted down, and reached out to test it as well. When he withdrew his hand, his fingertips were also covered in the same powder. The powder lingered on his fingertip for a moment before dissolving on its own, as if melted by body heat and seeping into the skin's surface. He looked down at his fingertips; what remained on his skin after the powder dissolved was a very faint gray mark with blurred edges, like old ink stains that had been soaked in water and faded naturally as they dried.
The Dragon Shadow hovered above the water's surface, its forehead glowing continuously, illuminating an area about two or three zhang in diameter beneath the surface. Within this area, Long Tian could vaguely see regularly arranged lines on the hard, flat surface at the bottom—like a paved foundation structure, partly covered by sediment and partly still visible. He picked up the oar again, slowly moving the boat along the edge of the structure. As it moved, the light spot continuously adjusted in sync with the boat's position, illuminating each section of the water beneath the surface it passed. The structure extended forward along a slightly curved line, stretching for about thirty zhang before narrowing at a certain point into a structural slit only about one foot wide, pointing precisely southeast. The edges of the slit were smooth, as if it had been chiseled open and then filled with fine material.
Long Tian stopped the boat at the location of the crevice. He placed the oar horizontally on the gunwale, and during this time, the Dragon Shadow receded from above the water to the height of the gunwale. The light seeping from the vertical line on his forehead lasted for about half a cup of tea's time before gradually narrowing, like a slowly closing gate gradually reducing its opening. After closing, it did not completely retreat into the interior of the closed line, but left a thicker vertical light trace on the surface of the closed line, like a crack in a door that still seeps a sliver of light through its edge after it has been tightly closed. The direction of the light trace was exactly the same as the direction of the structural crevice underwater, pointing southeast by south—the same direction he had seen previously on the dotted lines on the nautical chart and the patterns on the walls of the mountain hall.
He sat on the gunwale for a while. Yu Jin sat on the deck next to him, with a gap between them where oars rested. A gust of wind blew from the side, causing the boat to veer slightly. Yu Jin reached out and adjusted the rudder, reorienting the bow towards the light trail. The underwater hard structure maintained its outline beneath the surface, like a boundary line buried in the strata but not completely covered. Through the translucent layer formed above it by the water and sediment, it finally found a channel to sustain its existence between the continuous light and the continuous current, maintaining its course between the dark and light layers of water, like a landmark long overlooked on a nautical chart, finally read after a long period of silence.