The TAIC report, released today, found that the men fell from the lifeboat after one of the two wires attaching it to the ship failed.
The men were wearing safety harnesses but the wire holding the harnesses to the ship also failed during the accident.
Neither man was wearing a buoyancy device.
The lifeboat remained attached to the ship by the aft wire but suffered irreparable damage.
The accident also caused damage to the Volendam's hull which required repair before it could sail again.
Investigators found the wire holding the lifeboat was heavily corroded in the area where it failed, causing a loss of structural strength and a tensile fracture.
Maintenance of the wires had been hindered by the design of the davit _ the small cranes that hold the lifeboat to the vessel with cables.
Investigators found the design of the davits restricted access to the wire near the failure point, making it difficult to apply a protective coating of grease around the whole circumference of the wire in that area.
An inspection of the other davits on the ship found 10 wires were sufficiently corroded to require action.
The TAIC made urgent safety recommendations to the davit manufacturer, including to alert all operators of the davit system about the incident; to review the design of the davit system to remedy a tendency for the fixed arm to flex inwards under load; and to review other davit systems it manufactured to identify similar safety issues.
It said a key lesson was that a wire rope was only as good as its weakest point.
Thorough inspections needed to cover the entire length of a wire, and frequent and thorough lubrication was needed to prevent corrosion in a marine environment.
The TAIC also recommended taking the chance of a catastrophic failure into consideration when choosing a safety harness attachment point, and suggested personal buoyancy devices always be worn when crew were working over a ship's rail.
