Question 1

You're DPO on a DP2 diving support vessel with divers at 55m depth. Wind is 26 knots, ASOG yellow limit is 28 knots, red abort limit is 32 knots. The forecast shows the wind building to 35 knots within 90 minutes. The dive supervisor has 25 minutes left in the planned dive and asks if you can confirm the vessel will hold for that time.

What should you tell the dive supervisor and what should you do?

Accepted Answer

Inform the dive supervisor that you are currently Green but a forecast deterioration will likely bring conditions to ASOG yellow within 60-75 minutes — the dive team should factor this into their decision on whether to surface now or continue. Simultaneously inform the master of the forecast and the dive status. Do not wait for the yellow alarm to trigger before giving the dive team the information they need to make a safe ascent decision With divers in the water, the DPO's communication responsibilities extend to proactive information sharing — not just alarm-triggered notification. A 55m dive takes time to complete a controlled ascent and decompression. If the DPO waits for the yellow alarm before telling the dive supervisor, the supervisor loses planning time and may have to choose between a rushed ascent (decompression risk) and staying under while conditions deteriorate. Providing the forecast timeline allows the dive team to make an informed decision while there is still time to act safely. This is exactly the purpose of the ASOG's graduated alert system combined with good communication — not using alarm thresholds as substitutes for proactive situational awareness sharing.

Question 2

You're on DP2 watch during a cable survey operation. The ROV pilot requests you shut down the port aft azimuth thruster because its cavitation noise is interfering with the multibeam sonar. The thruster is currently not contributing significant thrust in the prevailing conditions. You shut it down.

What critical DP risk has this action introduced?

Accepted Answer

Shutting down a thruster changes the Worst Case Failure and may remove the vessel from DP2 compliance — the remaining thruster configuration must now be consequence-tested to confirm DP2 capability is maintained, and the ASOG status must be reassessed before operations continue Even a thruster contributing little current thrust is part of the vessel's redundancy configuration. Shutting it down may change which thruster now becomes the WCF, and the consequence analysis result for the new configuration has not been verified. IMCA 2024 incident data specifically recorded cases where DPOs deactivated thrusters in response to operational requests (noise, vibration, ROV interference) without reassessing the WCF impact — with some subsequently operating outside DP2 class capability without knowing it. The ROV team's operational preference cannot override the DP2 redundancy requirement without a formal reassessment and ASOG review.

Question 3

During a DP2 anchored-spread mooring operation, your two DGNSS systems begin showing positions that diverge by 4.2 metres and are moving further apart. The Fanbeam is not available at this worksite. Both DGNSS units show normal signal strength and differential correction status.

What is your immediate decision process?

Accepted Answer

With two diverging DGNSS units and no third reference, you cannot determine which is correct. Immediately inform the master, assess whether operations can safely continue with degraded reference confidence, and consider whether an additional reference source (taut wire, radar range/bearing, another DGNSS unit) can be deployed or activated before the divergence worsens Two reference systems that disagree cannot be arbitrated without a third — you simply cannot know which is correct. Averaging two potentially erroneous positions may drive the vessel toward the error. This situation directly mirrors the gyrocompass argument for having three units: with only two, a disagreement produces a binary uncertainty with no way to resolve it. The correct response is to treat this as a reference degradation event, inform the master, and seek a third independent reference before the situation develops. Operating near a mooring spread with an unresolved 4.2m reference discrepancy that is growing is a significant risk.