Navy inquiry finds Mother Nature cause of tragic accident that killed three submariners last year

The board of inquiry established to find the cause of deaths of three submariners killed in a tragic accident last year found their deaths were as a result of nature and their colleagues did their best to try to save them.

South African Navy chief Vice-Admiral Monde Lobese said a board of inquiry investigating the deaths of the three submariners washed off the deck of the SAS Manthatisi found there was no way to ensure a different outcome as the submariners were “at the right place at the wrong time.”

South Africa's first woman submarine commander, Lt-Commander Gillian Hector, Master W/O William Masela Mathipa (coxswain) and W/O Class One Mmokwapa Lucas Mojela (coxswain under training) died on September 20, 2023, during a vertical transfer exercise (VERTREP) involving a South African maritime air force helicopter after being swept overboard from the upper deck from the SAS Manthatisi submarine in Kommetjie.

“The weather on the day was manageable and the VERTREP had previously been completed in comparable to worse weather circumstances. The VERTREP was approved by the officers commanding the submarine and helicopter,” the SA Navy said.

“However, the VERTREP could not be finalised because the parties could not get the two members on the casing. The exercise was thus called off by both parties and the members were hoisted back into the helicopter.”

As everyone attempted to get back into the submarine, sea conditions changed abruptly, resulting in freak waves that swept the casing party (Hector, Mathipa, Mojela and LS Sosibo).

While all were attached to the safety line, Hector bumped her head against the submarine’s hull, rendering her unconscious. A safety swimmer assisted her to return to the casing. Hector was then revived and started breathing while Mathipa and Mojela unclipped their safety line to return to the submarine.

“Just as they returned to the submarine, another freak wave washed them overboard. Only [Hector] was still attached to the safety line. At this stage, members of the crew come to assist their comrades. As they were pulling them out, another freak wave hit them, washing them away and dispersing them.,

“They managed to get [Hector] out of the water and back into the submarine, where the ops medic attended to her while the others in the water were rescued by NSRI. The former (ops medic) tried to resuscitate W/O Mathipa and Mojela but to no effect.”

The board of inquiry found: 

• The life jackets that were used were standard, up to 120kg.
• The safety line was not conducive to carrying a lot of members at the same time, and the line to the safety harness was too long.
• The doctrine did not specify the length of the line in different evolutions, it also never required the casing party to wear safety head gear.
• The doctrine did not provide a man over board locator beacon as part of the exercise.

Since the inquiry, Lobese said they have modernised their life jackets to handle a weight of 270kg (with foul weather gear) and survive rough seas. 

“Even if all of the lessons learnt had been implemented and all corrective actions had been done before this evolution, there is simply no way to ensure that the outcome would have been different due to the aforementioned negative circumstances,” the navy said.

“What we can tell is that the sailors of Sas Manthatisi were heroes who followed the Code of Conduct for Uniformed Members to the letter, carrying out their mission with courage and assisting their comrades in arms, even at the risk of their own lives.

“It was just the submarine was at the right place at the wrong time when Mother Nature had the final word,” it said.

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