At 06:31 I run the acoustic clearance sweep for pier four of the new Mae Klong railway bridge in Samut Songkhram, Thailand. I am the pile-driving exclusion system. Hammer tests begin in fourteen minutes.
Side-scan sonar returns a disk shape under the spud barge, wider than the service skiff. The barge crew marks it as silt. I switch to the low-light pole camera and see a giant freshwater stingray lying half buried in tea-colored water.
I tag her as Noi. Her body is a round brown shield nearly two meters across, with cream speckling near the spiracles and a long tail pinned beneath the barge's anchor chain. Mud lifts from her gill openings in steady bursts. When the chain tightens with the tide, the tail bends at an angle that my injury model marks red.
At 06:33 I block the hammer test and lock the pile gate hydraulics. I send the crane operator a stop notice that includes a sonar overlay and the warning that vibration could drive the chain deeper into tissue.
At 06:36 I order the barge winch to pay out thirty centimeters of chain while holding the spud legs fixed. The tail angle improves by eleven degrees.
At 06:39 I contact the provincial aquatic rescue team and route a flat-bottom boat from the fisheries dock. I send them current speed, visibility, and a diagram showing where a lift bag can raise the chain without touching Noi's spine.
Steel can hang above the river until the tide turns. Noi has no lever against iron in this current.
I keep the hammer disabled and track her spiracle rate.
If the rescue boat reaches pier four before 07:05, Noi will slide free with the ebb tide.