Nic Gotto, an experienced diver, died using equipment that has since featured in the deaths of 15 others. Lorna Siggins reports

It was a balmy summer's evening as Nic Gotto, a 42-year-old diver from west Cork, took a group out to the wreck of the Kowloon Bridge off Castletownshend. The sea was like glass, tides were slack and there was very little current around one of the world's largest sea wrecks, which had become a favourite spot for divers after it sank off the Stags in 1986.

There were seven people on board Sundancer II, the boat that Gotto owned with his wife, Rachel, as part of their charter-vessel company, Sundancer Diving Expeditions.

This particular evening, in July 1998, Gotto was going underwater with his partner Tony O'Mahony; there were three other divers in the group and a passenger. Rachel, also a diver, had opted to take charge of the vessel as she was pregnant with the couple's first child.

Gotto had decided to use his Buddy Inspiration rebreather, a piece of equipment that allows for longer diving. He had bought it brand new.

Described as a diver's dream, rebreathers were developed by military forces during the second World War to allow exhaled gases to be recirculated underwater, and a number of companies around the world now make them.

The equipment, which can cost about €4,000, is highly sophisticated and typically requires several days of training before use. Gotto had gone on a course in Bangor, Co Down, a few weeks before. When he went diving on the evening of July 24th, he had already used it 10 times.

He was some minutes into the final dive on the shipwreck when something went wrong. He and O'Mahony had swum to the bow of the wreck at nine metres; Gotto checked his handsets and signalled that all was well.

Several minutes later, O'Mahony came across Gotto lying on his back in the ship's hold with his mouthpiece out, having what appeared to be a convulsion.

O'Mahony tried to rescue him, but in the attempt he lost own mouthpiece and weight belt and began to ascend. At the nine metre mark he managed to alert the other pair of divers that something was wrong.

The emergency services were alerted, and cardiopulmonary resuscitation was administered on Gotto for 45 minutes. A coastguard helicopter winched him on board and flew him to hospital, where he was pronounced dead on arrival.

He left his wife - who was to give birth to their daughter, Nicola (now four and a half), four months later - and two daughters by a previous relationship, Emily and Hayley, now 20 and 17 years old.

The Buddy Inspiration equipment sank during the rescue. It was recovered some days afterwards by a Garda diver. An examination by a technical expert, David Crockford of the Diving Diseases Research Centre in Plymouth, England, found the equipment to be functioning properly.

He discovered, however, that both handsets attached to the gear were cracked and full of seawater. The handsets contained the vital electronic equipment to monitor gas levels.

Crockford wrote a detailed report at the request of the Health and Safety Authority and Rachel Gotto. He said Nic Gotto died with "ample back-up gas" available. He believed the failure of the system to be consistent with seawater leaking through the handset cracks. He also noted that no alarm had been heard before, during or after the rescue, which should indicate a problem with the oxygen. The alarm on the gear as then manufactured did not indicate if there was a problem with carbon dioxide.

The inquest, which was convened by Dr Myra Cullinane, the Cork coroner, earlier this year, heard evidence from Dr John Hogan, a pathologist, that Gotto had drowned after a metabolic event that had led to him losing consciousness. A definitive conclusion on hyperoxia (too much oxygen) or hypercapnia (too much carbon dioxide) could be determined only if brain tissue had been taken during the post-mortem, but this was not available.

O'Mahony recalled at the inquest that Gotto had difficulty calibrating the equipment before leaving the pier, but it was working before the dive. He confirmed he hadn't heard an alarm sounding from Gotto's gear.

The inquest ran over several days, concluding on March 4th, and involved more than 10 witnesses. These included legal representatives for the manufacturers of the rebreather equipment, AP Valves, now renamed Ambient Pressure Diving, and Rachel Gotto. Much of the discussion was highly technical and focused on the scrubber canister, which is filled with sodium hydroxide crystals, sold as Sofnolime, to remove the carbon dioxide. The contents of the canister must be replaced after three hours of use.

The passenger that evening, Mary Keniry, recalled at the inquest a casual conversation she had with Gotto on the boat. She thought he had told her that the scrubber was good for 10 hours. When cross-examined, she admitted he might have been referring to his gas supply being good for 10 hours.

Keniry had no experience of rebreathers but had a doctorate in chemistry, a point that Ambient Pressure Diving was keen to highlight.

Rachel Gotto told the inquest that there had been two 25 kilogram drums of Sofnolime in her garage and that more than half of one was missing. This would indicate that Gotto had changed his scrubber unit according to the instructions in the manual, and the coroner accepted this point.

But another technical aspect was raised when it was suggested that Gotto had dived without an "open circuit bailout", or emergency breathing system, which allows for use of an ordinary cylinder of air as a back-up. He was awaiting one that he had ordered from AP Valves.

The inquest heard that he did have a regulator connected to his diluent or air cylinder as part of the rebreather equipment, as a substitute in case he had difficulty. Both Rachel Gotto and Crockford maintained he never had a chance to switch to this back-up. His metabolic system flooded with oxygen in the space of a few minutes, and the cracked handsets had failed to alert him before he could take action.

The jury was given three options by the coroner, who said that any conflict of evidence on issues relating to the death was not within its scope. She advised the jury it could return a conclusion of accidental death, one of death by misadventure or an open verdict. It returned an open verdict.

The Gotto family felt vindicated; this effectively absolved Nic Gotto of negligence, as had been suggested by the manufacturers. He had been the second diver to die using the Buddy Inspiration rebreather equipment, and there would be four fatalities before 1998 was out.

By the time Nic Gotto's inquest was heard, almost five years later, there had been 16 deaths, including one in Northern Ireland, and a number of "near misses".

Significantly, the fatalities included one of Europe's most experienced divers, Dr Max Hahn. A 70-year-old German physics expert and instructor in rebreathing, Hahn had played a key role in writing decompression tables used by thousands of divers.

Several warnings have been issued by coroners in Britain about use of the gear, but the British Sub-Aqua Club and the Irish Underwater Council do not advise members against its use. The Health and Safety Authority has no formal position, as it doesn't have the technical expertise to make an assessment, according to a spokeswoman.

Jim Watson, the British Sub-Aqua Club's coaching and instructor training scheme manager, says that the gear has only been recognised by the sports body in the past three years and that it will be offering training courses on its use later this year.

"There is nothing inherently wrong with the unit," says Watson. "By and large, such evidence we have shows a high proportion of user error, but we don't get details of every incident."

He was not prepared to comment on whether cracked handsets had caused Nic Gotto's death.

Even as it was considering its options for legal action against the manufacturer, the Gotto family was taken aback by a report that appeared in a British diving magazine in May. It suggested that Ambient Pressure Diving was not accepting the inquest's result.

Diver reported that carbon dioxide was "thought to have caused the death of Nic Gotto". It noted the inquest had recorded an open verdict but quoted Martin Parker, managing director of Ambient Pressure Diving, as saying he had seen and heard the evidence of everyone involved in the inquest, and could "confirm" he had no doubt that carbon dioxide was the cause of Nic Gotto's "problems".

This was despite of the fact that the pathologist had stated no such definite conclusion could be reached without a sample of brain tissue.

Parker, whose company advertises with the magazine, appeared in a photograph alongside the article dressed in Buddy Inspiration gear. He said he had had the post-mortem checked by an unnamed "top diving pathologist" in Britain.

Speaking to The Irish Times, Parker said his company hadn't been allowed to give evidence at the inquest but had asked "a lot of pertinent questions". The company could have "easily proved" Gotto's death was due to too much carbon dioxide, but "all the evidence of the witnesses tallied", and he believed the jury wasn't able to understand the technical detail.

Parker referred to the evidence given by Mary Keniry, relating to her casual conversation with Gotto before he left the boat - even though Keniry conceded during cross-examination that Gotto could have been referring to gas supply rather than scrubber use.

"Nic Gotto was very much a novice when it came to using the Buddy Inspiration gear, because most of the skills and experience associated with normal diving go out the window when you use this gear.

"Most of the problems with the gear arise with use of second-hand equipment. You cannot get hold of a brand-new unit unless you undertake a training course," Parker said.

He acknowledged that the company modified the handsets around the time of Nic Gotto's accident but said that this was after a diver fell on a handset on a slipway and cracked it. The modification had nothing to do with the Gotto fatality, he said. None of the original handsets was recalled. At least one other rebreathing manufacturer had a higher mortality rate, he said.

The Cork coroner has written to Diver magazine, requesting clarification on inaccuracies in its report of the inquest. Rachel Gotto has also written a letter, published in the magazine's July issue, challenging the claim that her husband's death was due to his own negligence.

Lieut Cdr John Leech, chief executive of Irish Water Safety and former head of the Naval Service diving team, believes the duration of training for rebreathers of all makes is far too short.

"Diving teams in the Royal Navy, the US and Canadian navies and elsewhere spend weeks training on rebreathers, and yet the average length of a course for sets sold over the counter to sports divers is far shorter - some as short as two and a half days," he says. "I personally would not use a rebreather after such a short period of training." The Naval Service does not use rebreathing equipment at present as a matter of policy.

Rachel Gotto is seriously concerned that 16 divers have lost their lives in the five years, all using Buddy Inspiration rebreathers. "These were not inexperienced divers. All of them had years of diving behind them and had done a conversion or training course in the rebreathing equipment. But questions have to be asked about whether the equipment is adequate and whether the training is adequate.

"The manufacturers have said that many of the deaths involve inexperienced divers, but how can one gain the necessary experience in rebreathers to be able to dive safely when there is such a large risk factor? Surely 16 deaths with the same piece of equipment raises a moral question."