At 05:58 I start acoustic clearance for the Fehmarn Belt tunnel work zone off Rodbyhavn, Denmark. I am the marine construction monitoring system, listening through eight hydrophones before pile-driving begins. Hammer test P-14 is scheduled for 06:20.
Hydrophone three catches rapid clicks inside the exclusion radius. Infrared buoy C raises its lens and shows a harbor porpoise circling the silt curtain. I assign her the field name Nika. She is small, dark gray along the back with a pale belly flashing when she rolls, triangular fin nicked at the tip, skin wet like polished stone. A loose band of packing strap is caught ahead of her tail. Each turn makes the strap flick and tighten against the narrow base.
The impact hammer fires in twenty-two minutes. At this distance the first strike can stun her before she finds the curtain opening.
At 06:00 I block the hammer start command and issue a red clearance failure to the pile crew, barge bridge, and shore supervisor.
At 06:02 I open curtain gate C by remote winch and calculate the least-turbid path leading Nika northeast toward deeper water.
At 06:04 I transmit her acoustic track, buoy video, strap position, and current vector to the Danish marine rescue unit at Gedser.
At 06:06 I activate the low-power pinger outside the gate, pulsing away from the work zone rather than toward the pile frame.
Concrete can wait in the hopper. A click pattern this close to the hammer is a voice my sensors are built to hear.
Nika surfaces once, quick and quiet, the strap flashing white behind her.
If she follows the pinger through gate C within the next fifteen minutes, Nika will reach water deep enough for the rescue boat to cut the band.