Diver trapped by Anchor Chain

What happened?

During diving operations to locate a pipeline end manifold (PLEM) near a single point mooring (SPM), a diver was trapped by an anchor chain.  The incident occurred when Diver 1, searching for the PLEM, went underneath the anchor chain without realising it.  His umbilical got caught and he turned back to find that it was trapped between the chain and the seabed.  He tried without success to free it, and then tried to pass back under the chain, which moved at that moment, trapping the diver at the chest and left shoulder.  Diver 2 was deployed to rescue Diver 1; he cut the umbilical and assisted Diver 1 back to the basket and safely back to the surface.  Decompression was not necessary owing to the shallow water depth (10-16m) and bottom time.

Diver 1 was diagnosed in the shipboard hospital as having suffered a minor thorax trauma and was discharged for rest.

What went wrong?

Investigation noted the following contributing factors:

  • Risk assessment and procedures:
    • hazard identification was neither suitable nor sufficient for the project
    • company manuals and procedures were not followed;
  • The client provided necessary information only at a late stage;
  • There were “adverse environmental parameters” – heavy seas were causing significant movements of buoy and chains;
  • The vessel was in the wrong place, and the vessel’s movements were inappropriate for the ongoing operation; i.e. the dive basket moved during dive while diver was on the bottom.

What actions were taken?

Our member took a number of detailed actions and recommendations which may be summarised thus:

  • More effective hazard identification (HAZID);
  • Ensure all necessary information for safe operations is available in a timely way;
  • Reiterate the full authority and responsibility of the Dive Supervisor in diving operations.