Localized Corrosion of Hull Structure Floods Vessel



On March 7, 2016, at 1000 local time, the 164-foot-long dive support vessel Hammerhead was discovered partially flooded with an increased aft trim while moored alongside the pier at the Newport Marine Terminal in Galveston, Texas. The vessel was in a layup period with no one on board. There were no reports of pollution. Damage to the vessel was estimated at $900,000.

The Hammerhead was built in 1972 by Burton Construction & Shipbuilding Company, Inc., in Port Arthur, Texas, and refurbished in 1998. At the time of the accident, the vessel was owned by Emerald O.V., Ltd., and operated by Ranger Offshore, Inc., a marine and subsea construction and support services contractor for the offshore oil and gas industry. Ranger Offshore operated a fleet of eight marine and subsea construction support vessels in the Gulf of Mexico and select international waters; the Hammerhead was one of four dive support vessels.

At left, the hole found near frame 31 of the bottom plating. At right, the screwdriver placed in the hole as a temporary repair. (Photos by Coast Guard)

Inactive since January 2015, the vessel had been moored for 15 months alongside the dock at the Ranger Offshore facility at the Newport Marine Terminal. On the morning of March 7, 2016, a Ranger Offshore employee making security rounds noticed that the vessel was sitting lower in the water than normal.

Draft readings were taken and reported at 6 feet 10 inches forward and 11 feet 11 inches aft, indicating that the vessel was trimmed 5 feet 1 inch by the stern. The surrounding water depth was charted at 13 feet. Upon boarding the vessel, the Ranger Offshore employee discovered that the engine room was partially flooded. He estimated that the water depth in the forward end of the engine room was 34 inches above the deck plates. No progressive flooding into other compartments was detected. The vessel was not equipped with a bilge alarm system that could be monitored from ashore.

At left, a Coast Guard inspector examines the condition of the port propeller. At right, marine growth on the port tail shaft. (Photos by Coast Guard)

Probable Cause

The National Transportation Safety Board determines that the probable cause of the engine room flooding of the dive support vessel Hammerhead was the localized corrosion of an aging hull structure resulting from the operating company’s lack of oversight and maintenance in preserving the hull’s metal plating with an adequate marine coating and cathodic protection system.


To protect vessels and the environment, it is good marine practice for owners to conduct regular oversight and maintenance of hulls, even during layup periods. Oversight should include monitoring the hull thickness, maintaining sufficient marine coatings, and using cathodic protection systems.

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