He exhaled. Not a mechanical failure. A calibration issue.

But the next sentence made his blood run cold: "Manual zero-point calibration requires access to Service Menu Level 3. See Appendix G for security access code."

"Any anomalies, Chief?"

He scrambled back to the laptop. He found the commissioning certificate buried in the PDF’s metadata. The shipyard: Gdansk, Poland. Latitude: 54° 21' N. He converted it to decimal degrees: 54.35. No.

Access denied.

The Service Menu bloomed open. He ran the zero-point calibration. The unit purged its sample line, flushed with clean seawater, and re-zeroed. The error code vanished.

Access granted.