Watchout: Slipping into sleep; drifting into danger

How one Master’s fatigue led directly to the grounding of a passenger vessel

What happened?

A small passenger vessel was running overnight trips for tourists from a home port. It had a small crew that worked a seven-day rotation before being relieved. On the evening of the sixth day, the vessel was being conned by the Master who was alone in the wheelhouse and sitting in the conning chair. He was feeling fatigued due to his heavy workload and was also taking prescribed medication. The Master initiated a turn to port, following his chosen route back to port. He then fell into a micro-sleep. As he was alone, no-one was there to rouse him and the vessel ran aground on some rocks.

The grounding caused a small hole below the waterline. This was not, however, judged to be a material threat to the vessel and incoming water was dealt with by a small bilge pump. Passengers were mustered, assessed for injuries and returned to the home port via fishing vessels. Investigations found that the incident was likely to have been caused by the Master’s high levels of workload-induced fatigue.

Why did it happen?

The Master was in sole charge of the vessel and, together with his crew, was in the sixth day of a seven-day rotation;
His sleep may have been broken by a range of interruptions, such as vessel movements and changes in the weather;
The Master fell into a micro-sleep while conning the vessel, caused by the effects of workload-induced fatigue. This was not mitigated against by his company’s SMS;
He was also taking prescribed medication that may or may not have caused side-effects, including drowsiness.

What lessons can be taken from this example?

Beware the dangers of micro-sleeping. If you can fall asleep at the wheel of a car, you can also do so at the con of a ship;
Standing and moving around while navigating makes it less likely that you will fall asleep, as compared to when you sit down;
Take ‘sleep hygiene’ seriously and always ensure that you are adequately rested before taking on navigational duty;
Be aware of the possible side-effects of prescribed medications.