Proassist III before the sinking. (Source: Proassist III Incorporated)

Proassist III before the sinking. (Source: Proassist III Incorporated)

Flooding and Sinking of Towing Vessel Proassist III

Investigation Details

What Happened

​​On December 24, 2020, about 1742 local time, the towing vessel Proassist III was transiting the Caribbean Sea, 3 miles off the coast, near Puerto Yabucoa, Puerto Rico, when its stern compartments began flooding. The three crewmembers aboard attempted to pump out the water but were unsuccessful and subsequently abandoned the vessel. They were rescued by a responding Good Samaritan vessel, and the Proassist III later sank about 0.25 miles from shore. No injuries were reported. An oil sheen was visible after the vessel sank. The vessel was later recovered but was considered a constructive total loss valued at $968,000.

What We Found

​We determined that the probable cause of the sinking of the towing vessel Proassist III was unsecured or open aft deck hatches, which resulted in the flooding of the vessel’s aft compartments from water on deck and progressive flooding to other compartments through openings in watertight bulkheads. Contributing to the flooding of the vessel was the owner’s lack of an effective hull inspection and maintenance program.​

Lessons Learned

Effective​ Hull Inspection and Maintenance

Over the past 5 years, the NTSB has investigated five casualties involving towing vessels whose weather decks and openings were in poor condition—leading to flooding and subsequent sinking. To protect vessels and the environment, it is good marine practice for owners to conduct regular oversight and maintenance of hulls, including between drydock periods, regardless of inspection requirements. An effective maintenance and hull inspection program should proactively address potential steel wastage, identify hull and watertight integrity deficiencies, and ensure corrosion issues are repaired in a timely manner by permanent means.​


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