The death of trainee diver Zachary Yarwood revealed a poorly governed navy dive school with a culture that pushed students beyond their limits. TONY WALL reports on systemic failings that led to a tragedy.

A week before he died, able diver Zachary Yarwood had become exhausted during a mud run and pulled out of a dive planned for immediately after the event.

Yarwood had been doing well on his dive course – he would often take charge of the students – but had struggled with some of the cardiovascular activities and was under pressure to improve his underwater endurance.

A Court of Inquiry report into his death found this was the background leading to Yarwood and other students using a highly dangerous and unauthorised gas-switch procedure in an effort to improve their dive times – a move that caused his death.

The report lists a catalogue of failings within the dive school system at the time of the incident on March 25 last year, including a lack of governance, a culture focused too heavily on physical prowess, poor risk assessment and fatigue management systems and confusion around dive instructions and policy.

On the night of the fatal dive there were not enough staff attending and two of the instructors did not have all the required qualifications.

The attendants were supposed to have eyes on the floats marking the divers’ underwater progress at all times – at one point one of them left to make a cup of tea.

The inquiry found that students felt pressure to impress their instructors by increasing their dive times. The court recommended the school move to a more “adult learning environment”.

In additional comments attached to the report, the chief of navy, rear admiral David Proctor, questioned the focus on building underwater endurance and said he was concerned with the priority placed on physical prowess.

“The navy diving culture needs to be adjusted,” he wrote. “Perhaps a culture more aligned to dive professionalism, humility and mission achievement today and tomorrow would be more appropriate.”

Stuff obtained a copy of the inquiry report from Government sources, ahead of sentencing next month of the New Zealand Defence Force on charges of failing to ensure the safety of employees. It pleaded guilty and faces a maximum fine of $1.5m.

The Defence Force says it won’t comment on the Court of Inquiry report until after sentencing.

Meanwhile, police are continuing their investigation into Yarwood’s death and are appealing for witnesses to come forward. “We believe that there may be current or past members of the Navy Dive School who may be able to assist the investigation," says Detective Rebecca Foote of the Waitemata East CIB.

Yarwood's family declined to comment, but have previously said they want the navy held accountable.

Yarwood was only 23 when he died in hospital with hypoxia the day after being pulled from the water, unconscious, during a night-time dive drill, but was already something of a navy veteran, having joined in 2013 as a communications specialist.

He had become bored with that role and was training to become a diver, considered by sailors to be one of the elite jobs in the navy.

Yarwood was fit and strong and heavily muscled, which is likely to have increased his demand for oxygen when diving and contributed to his perceived poor endurance.

The court heard the chief instructor felt he was not giving 100 per cent, which was raised with Yarwood in a performance meeting.

This wouldn’t have sat well with him, the report says, as he was highly driven and determined to be the best.

Three days before the incident an instructor had told the students fatigue was no reason not to dive, a comment which is likely to have weighed on Yarwood, says the report, as he had pulled out of the dive following the mud run.

Yarwood’s last day began with a 6km run at 8am.

The first dive was at 9am – an oxygen compass swim – followed by lunch and then a mixed gas dive in the Calliope Dive Basin at Auckland’s Devonport Naval Base.

The final mixed gas dive, where the students take two gas bottles – one oxygen and one a nitrogen/oxygen mix called nitrox – began at 8pm.

By the time Yarwood was pulled from the water the students had racked up about 390 minutes (six-and-a-half hours) of dive-time – considered a heavy load. Changes that came in two months after Yarwood’s death prescribe a 300-minute daily maximum for nitrox rebreather diving.

The night dive involved a snag line search of the seabed, using Drager LAR7000 rebreather equipment used by militaries around the world for shallow diving.

The depth was about six metres and visibility was nil because it was night and the bottom was muddy.

The six students were split into two groups of three and were diving either side of a pontoon near the HMNZS Matataua.

The technique involved two divers secured about 30m apart on a guideline called a jack stay, with a roving third diver swimming in between unsecured, holding the snag line by hand. Yarwood was one of the roving divers.

Each diver was attached to a float line to the surface, which should have been monitored by two attendants. The court heard there were none that night, a breach of regulations.

The dive supervisor, a standby diver and a medic were the only staff in attendance and were having to fill multiple roles, including manning the safety boat while also keeping an eye on the floats.

The report says the lack of staff meant it was essential for the supervisor and standby diver to remain at the dive site during operations.

But the supervisor allowed the standby diver to go and make a cup of tea, although the diver claimed to still be able to see the floats.

The court heard that the dive supervisor and standby diver did not have all the required qualifications for diving with mixed gas and hadn’t completed a classroom instructors course.

The supervisor said he hadn’t received any formal orientation or induction into his post, was “thrust into the role at short notice and had to work out what needed to be done himself”.

The report says there was no evidence he had read and understood the various orders and instructions he was subject to.

“It is of concern to the court that in an area of hazardous activity the instructors present that night, and possibly the remaining staff at the school, have not completed the required instructional training,” the report says.

“Much of the information related to currency of qualifications appears to be haphazard and fragmented, suggesting it is not easily accessible or trackable.”

The court found that the prime cause of Yarwood’s death was a procedural violation it described as a “gas switching trick” to save gas and increase endurance.

The other students admitted they had been switching the LAR7000 rebreather between nitrox and oxygen modes without authorisation, when they should have stayed in mixed gas mode.

The practice involves closing the bubble diffuser and allowing the counter lung bag to fill up.

When the bag is full the diver switches from nitrox constant flow mode to oxygen mode. The diver then breathes from the bag, trying not to activate the oxygen demand valve.

The diver continues to breathe mixed gas from the bag until it is depleted and switches back to mixed gas mode based on a judgment call.

Evidence was heard that Yarwood had introduced a variation, by turning off the oxygen cylinder to avoid tripping the oxygen demand valve. When his equipment was recovered the oxygen cylinder was in the off position.

The report says various theories were put forward for this, such as someone tampering with his equipment, but the court was satisfied Yarwood turned it off himself, probably so instructors wouldn’t discover he’d used too much oxygen.

The students admitted they’d used the gas-switch trick on the second dive of the day and the report says it appeared to have helped with their endurance, as they’d beaten their previous records. Theirs was the only course using the trick, and Yarwood may have been one of the instigators.

The students talked about the practice during the day of the incident and some, including Yarwood, had said they’d felt dizzy and unwell while doing it.

A medical dive specialist told the court someone could become hypoxic in minutes by doing the procedure and not even know it.

He described the practice as “extraordinarily and unbelievably dangerous” and feared it was a hidden danger with “highly motivated” young men.

“They just try anything to appear to be good at what they’re doing and being good at diving is sometimes interpreted as using the least gas,” the specialist told the court. “The way we do business sometimes inspires perverse competitive behaviour that can result in events such as this.”

One of the students told the court: “None of us knew how high the risks were.” The report says it appears they had more fear of being caught than getting into difficulty.

The report says that as a slightly older, experienced sailor, Yarwood most likely felt pressure to improve his times more than the others. He had the lowest dive times on the course.

“He had worked hard on his physical abilities, took dive training very seriously, was always keen to be the best. In the court’s opinion his relatively poor dive endurance is likely to have weighed on him heavily.”

The students were 88 minutes into their night dive when things went terribly wrong. One of the groups got into difficulty with tangled lines and the supervisor directed all divers to surface.

The supervisor and standby diver were assisting the first group when they noticed only one diver from Yarwood’s group had surfaced. They pulled up in the safety boat as another diver surfaced, splashing the water to indicate a diver in distress.

One of Yarwood’s companions found him prone on the bottom and thought he was “messing around”. He realised he was in trouble and largely by feel, brought him to the surface, which was difficult because Yarwood was much heavier than him.

It’s thought Yarwood could have been unconscious underwater for around 15 minutes.

He was tangled in lines which needed to be cut before moving him to the safety boat and then the pontoon.

There was blood coming out of his mouth, which made it difficult to insert an airway device.

The standby diver did CPR until ambulance staff arrived and intubated Yarwood. A pulse was recovered and he was taken to North Shore Hospital, but he had suffered severe brain damage and died the next day.

The report says that it’s possible the supervisor and standby diver became distracted attending to the first group of divers and didn’t detect there were problems with the other group until they surfaced, although the staff denied this.

The lack of staff may have also contributed to a delay in contacting emergency services as they were all involved in recovering Yarwood, the report says.

“The court determines that a prime objective of all underwater training should be the ability to effect immediate rescue, if required, of inexperienced rebreather divers,” it says.

The court says the navy should “seriously consider” not allowing trainee divers to swim solo, and pair them with a short buddy line.

“The ideal would be to have an instructor in the water.”

It made a string of recommendations around governance and policy and said the dive school needed to focus on technical mastery of diving and dive safety, moving away from the “old school” attitude that the course was a “rite of passage” or a proving ground.

Proctor says in his statement the loss of a sailor during dive training is unacceptable.

“This tragic accident has highlighted that the dive training system and wider (Defence Force) diving system, requires corrective actions be undertaken to ensure that the lessons from this accident are addressed in a timely manner.”