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Divers vs. Tugboat

2016
Jul 19

Incident narrative

A habitat evaluation dive was planned for a shipping channel leading to a naval base. The Divemaster coordinated with the port operations office in an effort to avoid diving during the transits of large vessels. During the dive, a tug proceeded up the channel and came too close for comfort to the dive support vessel. As the tug approached, the Divemaster sounded the recall for the divers. The tug ignored several calls on VHF Ch 16 and the prominent dive flag displayed by the dive support vessel. The divers heard the recall and were ascending when they heard the noise from the approaching tug. Rather than surface in an unknown situation, they descended to the bottom and waited for the tug to pass. They then made an uneventful ascent and were recovered by the support vessel.

Findings

The tug was scheduled and the Divemaster was aware of the window in which the tug was expected, however it arrived early. The dive support vessel was unable to communicate with the port operations office or the tug due to confusion over which radio channels were being monitored. The port operations office was confused about the dive site because they were given coordinates in a format they did not understand (degrees, decimal minutes vs. degrees, minutes, seconds).

There were several dives planned for the day and the ship channel dive was the deepest. The order of the dives was made to conduct the deepest dive first in spite of the expected close timing to the tug transit.

Lessons learned

  • When developing dive plans involving coordination with non-diving activities ensure that communications protocols are clearly understood by all parties and tested. If someone says they will be monitoring Ch 16 and 82a, they will not mind a simple radio check from your boat to make sure communications are working.
  • Make sure your dive sites are known to other parties; look at their charts to make sure they mark the correct spots. The conversion from 24.75’ to 24’ 45” is not difficult, but do not assume everyone can make it.
  • Lastly, planning your dives with the deepest one first is a suggestion, not a requirement. It does allow you to minimize surface intervals and improve productivity, but there is no physiological safety benefit. In this case it would have been more prudent to make one of the shallower dives first and make the channel dive further away from any scheduled ship transits.

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