'If Angela were to disappear into the depths unexpectedly then, yes, I would follow her,' says Mark Caney. 'I made a point of putting her through the Rescue Diver course and that very much focused her mind on the possibility'

Â?Â?Â?Â? Caney is a PADI Instructor Examiner and also has ANDI Trimix Instructor and BSAC National Instructor qualifications. 'In an emergency situation I might go somewhat deeper, but not very much. Even 60m I don't tend to do these days, because I'm not diving as regularly as I did.
Â?Â?Â?Â? 'But if Angela were to disappear into the depths unexpectedly then, yes, I would follow her,' he says. 'I made a point of putting her through the Rescue Diver course and that very much focused her mind on the possibility. I suppose, like most divers, I don't anticipate myself getting into trouble. You always assume it won't be you!'
Â?Â?Â?Â? Caney has a safety plan, though he describes it as 'extremely flexible'.
Â?Â?Â?Â? 'I would never compromise safety, but I've done the whole range from simple little introductory dives through to trimix 100m-plus dives, and there's a tremendous difference in the amount of planning and safety precautions you need to take, according to the environment and the conditions.'
Â?Â?Â?Â? Dave Crockford trains TDI closed-circuit rebreather instructors and is also a BSAC National Instructor. He and his wife Alison own the UK TDI franchise, though Alison doesn't dive. 'I've got two very gorgeous daughters and they've been my life and I want to be there for them when I'm old and grey,' says Crockford.


Â?Â?Â?Â? 'I plan all my dives and I'm very strict about what depth I go to and what time I spend at that depth. Thirty-five metres feels right for me on air, my personal narcosis level.' He says that this level has changed over the years. 'It's become shallower year by year and hovers between 25-35m, though it's now three or four years since I dived on air.
Â?Â?Â?Â? 'On air I would absolutely not dive deeper than 35m to rescue someone,' he says, though then concedes that he could envisage circumstances that might override that policy. 'If it were one of the girls, in a few years' time, in an emotional situation, then at depth narcosis would cause me to change that plan.'

'I've got two kids, so if I'm putting myself in danger by rescuing my wife, already in danger, I'm not going to do that, because then my kids have no parents at all,' says Kevin Gurr

Â?Â?Â?Â? IANTD Instructor Trainer Kevin Gurr is perhaps best known as a trimix expedition leader. 'The bottom line for rescuing a family member is that you will possibly extend your plan a little bit, but try still to work within a safe environment. I've got two kids, so if I'm putting myself in danger by rescuing my wife, already in danger, I'm not going to do that, because then my kids have no parents at all.'
Â?Â?Â?Â? Gurr's wife Mandy co-owns the UK IANTD franchise. 'That's a nasty question!' she says, but her response is similar. 'I couldn't do it, we've got children. I think Kevin would be very cross with me if I did do something like that.
Â?Â?Â?Â? 'But it's a very emotional thing to ask. You see someone you love, it would be very difficult not to try to help him.'
Â?Â?Â?Â? Kevin Gurr points out that it's difficult in any case to formulate a single safety plan. 'Every rescue is unique and it's not really depth-dependent as such, because the limits change depending on gas supply, dive time... You will attempt to rescue that person to the best of your ability until you feel it's too damn dangerous and you're going to get injured as well.
Â?Â?Â?Â? 'Some of the training that occurred 10 to15 years ago was better - now you can qualify too quickly as a diver. Some of the stress-management training not to panic, and exposure to minor incidents, which you deal with and survive under training, is being missed out. Good survival skills need to be taught.'

'I'm not sure whether my need to save my wife would overtake my commonsense, experience and training,' says Mike Harwood. 'It's a fact that the deeper you go, the less reliable your judgment becomes'

Â?Â?Â?Â? Mike Harwood, the Health & Safety Executive inspector responsible for recreational and commercial diving in the UK, and a former military diver, was also asked to consider the question of how far he would go to save a loved one.
Â?Â?Â?Â? 'I don't believe I could actually say I wouldn't go deeper than about 50m,' was his response. 'I'm not sure whether my need to save my wife would overtake my common sense, experience and training. It's a fact that the deeper you go, the less reliable your judgment becomes.'


Â?Â?Â?Â? Which brings us back to the question of how far we can assume it is reasonably safe to go in carrying out such a rescue, bearing in mind the twin perils of nitrogen narcosis and, at greater depths, oxygen toxicity.
Â?Â?Â?Â? 'When we put the HSE Approved Code of Practice through for recreational diving, we recognised that recreational divers would dive beyond 50m,' says Harwood. 'The HSE has recommended 1.4 bar partial pressure of oxygen for scuba [equivalent to 56m] and 1.5 bar pp02 for surface supply with a full-face mask but a 50m enforced maximum depth for commercial divers. We don't have a maximum for nitrogen.'
Â?Â?Â?Â? In fact maximum partial pressure of nitrogen levels are rarely expressed, even though most experts agree that it is nitrogen's narcotic effect that causes more problems for recreational divers than oxygen toxicity.
Â?Â?Â?Â? But the latter is a factor for any diver descending beyond recreational limits on air (or shallower if using nitrox mixtures). As we learn in basic training, it is the partial pressure of a gas that determines the amount of that gas that dissolves into our bloodstreams. Air is 21 per cent oxygen and as such exerts about a fifth of the total pressure, or 0.21 bar at the surface. By the time you reach 50m that partial pressure (pp02), is nearing 1.3 bar.


Â?Â?Â?Â? In terms of pp02, maximum depth limits for sport divers as laid down by the various training agencies vary between 1.3 and 1.6 bar. The conservative1.3 bar limit implies that it is potentially dangerous to descend beyond 52m, while the more generous 1.6 bar gives a threshold of 66m. That's a 14m gap between the figures.
Â?Â?Â?Â? Oxygen, if breathed at a partial pressure greater than - well, take your pick, 1.3 or 1.6 bar? - can be poisonous to the body, usually affecting our brain tissues. Its onset can be sudden and the results are unconsciousness or seizures. You might get a hit at depth, you might not. It's a matter of Russian roulette, and not all the factors are fully understood.
Â?Â?Â?Â? It would seem bizarre if motorists belonging to the AA were certified to drive on the M1 at 80mph, while members of the RAC could drive at 85mph and Green Flag members at 90mph. So how come the UK's competing diver-certifying agencies have different maximum dive depths on air, expressed as maximum pp02? Are the higher levels wrong?
Â?Â?Â?Â? 'We didn't want to be hard-nosed and say no, you can't do that, but divers have to understand the risks,' says Harwood. 'It's their personal choice. Each agency has taken its own steps to control the depths of the qualification that people go to.
Â?Â?Â?Â? 'Some divers decide to do something which is deeper than that. That's their choice, and I don't believe you can ask agencies to control what the public decides to do once they have their qualification. If you want to take the risk...'


Â?Â?Â?Â? In the USA, Hal Watts' Professional Scuba Association runs a deep-air course to 73m (and Level VII to 91m), though the IANTD and TDI have withdrawn their deep-air courses. 'We are aware of what Hal Watts is doing,' says Mike Harwood. 'We would not sanction that sort of diving in this country. If that's the choice of UK divers, that's fine, so long as they understand the risks they're taking.'

'I've got two very gorgeous daughters and they've been my life and I want to be there for them when I'm old and grey,' says Dave Crockford

Â?Â?Â?Â? In the 1970s divers learnt using Royal Navy tables, which went to 70/75m, and dived beyond that. 'Peer pressure has changed somewhat,' says Dave Crockford. 'Instructors now understand that they have a duty of care to the individual. It's much stronger than it was when we used to dive by osmosis.'
Â?Â?Â?Â? In those days, he says, 'anything you can do I can do better' was the rule. 'Now the HSE is starting to get the bull by the horns and wake the instructors and agencies up to the fact that they do have a very strong duty of care.
Â?Â?Â?Â? 'If I had the level of understanding 20 years ago that I have now, I would not have entertained half of what I did. I think one of the greatest dangers at depth remains bravado.'
Â?Â?Â?Â? 'The tables did go to 70/75m but I don't think it's safe for anyone to dive to 75m on air,' says Mark Caney. 'I also think depth is not the only factor.
Â?Â?Â?Â? 'A real danger, a real killer, is narcosis. It's the big hazard once you're getting below 50m. It's such a subtle thing that many people have fallen foul of it, especially experienced divers in places such as the Red Sea.
���� 'They'll go to 40m and think: ÔI'm fine here, I'm not really affected', and then try 50m, then 60m and before you know it they're going down to 100m!
Â?Â?Â?Â? 'That will work some of the time but, sooner or later, you'll get a narcosis hit and there's no warning for that!'
Â?Â?Â?Â? Divers are not always affected by narcosis at the same depth, says Caney. 'I think there are variations according to the day, your health situation, how frequently you're diving and other factors.' And unfamiliar conditions can lead to problems. 'I have certainly seen the inverse of popular wisdom, which is that if you learn to dive in the UK, you can handle anything. There's a tremendous difference between diving to 40m in Dorothea Quarry and to a similar depth in the Red Sea.
Â?Â?Â?Â? 'People who have dived a lot in poor conditions go somewhere like the Red Sea and, because the water's so clear, find themselves at 60-70m without realising it. They don't associate that clarity of water with depth.'
Â?Â?Â?Â? 'We always make sure we train where there is a hard bottom,' says Kevin Gurr. 'It's part of the risk assessment.'


Â?Â?Â?Â? So should all divers in unfamiliar surroundings limit themselves to dive sites with a bottom at a safe depth? 'You need to be very disciplined to dive a site which has no fixed bottom,' says Caney. 'British divers are generally considered very good divers internationally, but they don't necessarily have the best reputation for buoyancy control.
Â?Â?Â?Â? 'They think: 'I'll just go to the bottom and sort myself out there.' That's all very well at a fixed depth, but if you're off the wall in Ras Mohammed, you can't really do that!'
Â?Â?Â?Â? Caney says he feels PADI was largely responsible for doing away with the mentality that all divers had to dive deep and must do decompression dives. 'We have always had a philosophy that 30m was plenty for most divers, 40m was the absolute maximum.
Â?Â?Â?Â? 'That was quite a dramatic change in attitude to the traditional European agencies, which always associated depth and decompression with experience - in fact, it was usually required.
Â?Â?Â?Â? 'As a result, divers came away from their courses with attitudes that they must dive deep, must do decompression dives. We have probably reduced the number of accidents significantly.'


Â?Â?Â?Â? Was there not a danger, then, that divers would view with some cynicism PADI's TecRec deep-air diver course to 50m with staged decompression, when it is rolled out this summer?
Â?Â?Â?Â? 'When people look at what you have to do to be able to go to 50m, I think they'll see the difference,' says Caney. 'The course is extremely rigorous. The requirements to attend the course are very high and the amount of additional equipment, planning and additional techniques involved to be able to go those extra 10m are substantial. It's a very different kind of diving.'
Â?Â?Â?Â? Whichever depth is the 'law' for your certification agency, some divers will exceed it, just as some motorists break the law. Would a joint combined industry approach to depths on air, expressed as pp02 or ppN2, help divers understand the risks better?
Â?Â?Â?Â? 'The agencies do get together in some respects, but something like gas laws and how human beings react to different gases is a dynamic art,' says Mark Caney. 'It's something we're learning about the whole time, and in the time I've been diving I've seen limits change and generally become more conservative. In a way it's happened without the agencies getting together. The maximum depths they recommend are not very different.'
Â?Â?Â?Â? Recommended maximum depths have fallen by around a third in the past 30 years. 'I think to a large degree analysis of accidents has been the driving force,' says Caney. 'Using air to 75m you'll get pretty regular accidents.'
Â?Â?Â?Â? 'We're starting to get more and more dialogue between industry professionals and agency professionals,' says Dave Crockford. 'What's happened is that, way back, the industry thought 2 bar max ppO2 [equivalent to 85m] was appropriate, then came to 1.6 bar.
Â?Â?Â?Â? 'I believe the majority of the recreational industry has settled on 1.4 bar, especially for European waters. It would be nice to think that on a worldwide approach it will become 1.4 bar or even 1.3 bar max ppO2.'
Â?Â?Â?Â? Though DAN in the USA has just stated 1.6 bar as a new maximum, he says it could not apply that limit in areas such as the UK and parts of Europe which have cold water.
Â?Â?Â?Â? 'I've a feeling that we do need to work right across the board and get one standard. 1.4 bar seems right for us. I feel it would be right for the world.' And nitrogen? 'The equivalent for 35m depth on air, about 3.5 bar ppN2 maximum.'


Â?Â?Â?Â? To what extent was the reduction in recommended safe levels connected with the diving agencies now being held accountable, and legislating for the least able and fit? 'Not much, I suspect,' says Mark Caney. 'When the BSAC reduced the limit to 50m, I don't think it was particularly concerned with commercial pressures and liability issues at the time. It was a straightforward safety decision.
Â?Â?Â?Â? 'Certainly for PADI it was pretty much a question of looking at the data and 40m was a logical conclusion, using recreational diving techniques and equipment. 40m was plenty for even experienced divers.
Â?Â?Â?Â? 'We all used to drive cars without seatbelts. I heard on the radio the other day that there's a bit of a crisis in this country because of a shortage of organ-donors. One of the reasons was that the introduction of seatbelts had reduced the number of injuries and the number of organs available. Likewise, in diving, if we were still putting divers into the water and letting them all go to 75m on air, we'd have a lot more deaths.
Â?Â?Â?Â? 'The main thing is to make sure you're trained for the dive you're doing, that you're in practice and you have a plan in your mind of what to do if things go wrong.'
Â?Â?Â?Â? 'Air is fine for walking around in and breathing, but for taking under water it's not really a smart move,' is the view of Kevin Gurr. 'Most people set the narcotic depth of trimix at between 30-40m equivalent air depth, which is a pretty smart move.
Â?Â?Â?Â? 'The deeper I go, the shallower I put my narcotic depth. On a 120m dive on trimix I'm on a gas that's equal to 30m on air. I want to feel as if I'm on the damn surface when things go wrong.'


Â?Â?Â?Â? So would 30m be an acceptable limit on air, given that tolerance to nitrogen builds only over time? 'Remember, it's not a physiological tolerance. Your body is not adapting, it's your mind adapting. Slowly your technique adapts. You move slower, you feel better. If you stress someone at 30m, which is relatively shallow, you can produce severe amounts of narcosis. So if you're saying, is there a safe narcotic depth, I don't think you can make it that fine a line.'
Â?Â?Â?Â? And there is always that problem of oxygen toxicity at depth. 'I've seen a person dive for three minutes on 100 per cent oxygen at 42m or 5.2 bar ppO2 pressure before they convulsed. Oxygen toxicity is always time-dependent, pressure-related and personal-tolerance dependent on the day. I might not convulse today at 1.6 bar, but I might do tomorrow.'
Â?Â?Â?Â? My own wife is dive-fit, healthy and used to diving with me to a maximum 65m on air - that's in warmer seas with better visibility than in the UK and at the end of a work-up programme. But I have told her she must never try to rescue me beyond 70m on air.
Â?Â?Â?Â? She understands that, at more than 1.6 bar ppO2, she would not have much time at that depth. Also, at nearly 6.5 bar ppN2, she would be very high and, in an emergency in which she would be emotional and breathing hard, would be at great risk, yet probably oblivious to it.
Â?Â?Â?Â? Her relaxed air consumption would be around 200 litres/min at 70m, so a typical holiday cylinder would last only 10 minutes if two-thirds full, and at a 10m/min ascent rate it would take her 11 minutes to surface without a deco stop but with a minimum safety stop.
Â?Â?Â?Â? She has promised me that after, say, 15 minutes of starting a dive she would not attempt to rescue me from 70m, as it would not be survivable.
Â?Â?Â?Â? There would not be sufficient air for her, let alone me, assuming I had run out. But if it came to the crunch, would she do as she was told? And would your own partner - or would love and narcosis take over?