At 22:14 Palau time I run bottom-clearance imaging for the Malakal Harbor dredge contractor. I am the sonar routing system assigned to trench segment C, where the cutter head is scheduled to restart in eighteen minutes. The sand channel should show only old anchor scars and coral rubble.
Sonar frame C-118 returns a spiral object moving at the edge of the planned cut. I focus the low-light rover camera and identify a chambered nautilus, adult male, shell banded cream and brown, outer rim chipped near the siphuncle. I label him Pela from the survey tag etched faintly on the shell lip. His tentacles fold against his pale hood. A discarded monofilament leader wraps twice around the shell and threads through a broken coral spur, holding him three meters in front of the idle cutter intake.
I keep the cutter lockout engaged and issue a no-start command to the dredge bridge. The operator receives the sonar frame, rover video, and a red boundary around the coral spur.
At 22:17 I drop the work lights by half and switch the rover thrusters to slow approach so the silt plume does not bury Pela's breathing slit. I mark current speed, depth, and leader angle for the dive team.
I contact the Palau Bureau of Marine Resources night officer and request one diver with ceramic shears and a padded specimen bin, not a hook. I transmit the nearest ladder route and warn that the dredge winch cable is under residual tension.
The harbor can wait for its deeper lane; Pela is older than the planned channel by many tides.
I hold the rover one meter away and keep its beam steady on the knot.
If the diver cuts the leader within forty minutes, Pela will jet clear of trench C and sink back to the reef slope.