The other day, I came across a question on a divers’ chat room: “My boyfriend is doing a nitrox course. Should I do the course with him? I do not need it as I always have at least 1500 psi left in my tank at the end of a dive when he is down to 500 psi.”

There is so much to unravel in this question. It shows how, even now, after nitrox has been widely available to sport divers for almost 30 years, there is still a lot of confusion about what it is and what it does.

Sometimes, an instructor will acknowledge that what they are teaching is not what they actually do themselves. How many times have you heard an instructor say, “I have to cover this, but it is not how it really works” or “The manual says this, but in the real world, we would do something different.”

It is even worse when the instructor insists that a procedure is absolutely essential, but when they go diving for themselves, they skip it or do something completely different. This is a very dangerous trend in teaching.

I also outlined a defensive diving strategy involving how to use your dive computer. Here are a few more strategies that I see as intrinsic to the defensive scuba diving concept, where “defensive” carries the same meaning as in the motoring world, that is: safe, careful, conservative and thoughtful.

Avoid the “normalisation of deviance” pitfall

In a nutshell, normalisation of deviance is having a safe procedure, then cutting a corner on this procedure and continuing to cut the same corner until it becomes routine and you rationalise that the corner-cutting makes sense.

Subsequently, as we do more diving, we gradually improve our skills and we experience various problems. By achieving mastery of the skills and dealing with the issues we encounter, we acquire the ability to anticipate problems and to avoid or manage dangerous situations.

As you might recognise, this is similar to the process of learning to drive a car. In diving as in driving, however, what guarantee is there that experience will teach you everything you need to know?

Human factors is usually considered a way to make diving safer, but it actually goes far beyond that and can be used to great benefit to maximise individual and team performance and get much more out of diving.

The world of human factors is huge, so this article will focus on a few subjects that come under the human factors umbrella. Besides offering some specific guidance, it will hopefully provoke some thought into how you might apply the concepts to your own divemastering style.