While dodging* in the vicinity of a North Sea oil field, my Platform Supply Vessel (PSV) was heading 060°T at 1.5kts. a cargo vessel was heading 102° (T) 11kts, approaching from abaft my port beam and passing very close, Closest Point of Approach (CPA) 0.175m. to this vessel and close to the whole rig operation. When challenged on VHF 16, the Officer of the Watch of the other vessel altered 5° to port to pass close between my vessel and another PSV one mile away. The OOW of the other vessel did not appear aware of the rig-shift which was notified on Nav-tex for the previous two days.
(*The reporter subsequently clarified that “dodging” is steaming at very slow speed into the weather whilst awaiting orders. The PSV’s were not connected to the rig at the time.)
We passed a disidentified copy of the report to the manager of the cargo vessel. Soon after, he sent us a reply from the OOW as follows:
I was indeed heading 102 degrees. In good time I observed 2 PSV’s which were laying still with a distance of 1 nautical mile between them. I made the decision to go between them leaving approximately 0,5 nautical miles to each PSV. As I came closer I observed that the PSV more to the south was making 1,5 knots, heading 060 degrees. I was contacted by the PSV that he was concerned about our CPA and I made the judgement, based on the fact that the PSV did do 1,5 knots and the clear visibility and good weather conditions, that a course alteration to port of 5 degrees would leave me an satisfactory CPA to both PSVs. Because the PSV did not contact me again I reckoned that my action satisfied the PSV also. At no time did I experience that this was a close quarters situation. I am sorry for any inconvenience my actions may have caused the reporter on the PSV.
We thank the reporter for sending us the report, the manager of the cargo ship for following it up promptly and the OOW for his open response and apology.
This is an example of an incident in which there was a different perception on the bridges of the vessels as to what constitutes a reasonable margin of safety. There is not an absolute answer to this as it depends on the circumstances. Close passing may well be inevitable in confined waters but would cause concern on the open sea. CHIRP‘s request to Officers of the Watch, and indeed to those in control of any craft, is to bear in mind how your action, or inaction, will be perceived on the other vessel. In applying the Regulations for Preventing Collisions at Sea, let’s try to avoid causing anxiety to others.
We also add that information from Nav-tex should be included in the passage plan and noted on the chart.