And this invalidates DIR as a system... why?
What I, and others, said is that DIR simply cannot be done for
many types of diving that people want to do.
Side-mount (or no-mount!) cave diving is an example; you can't meet the "DIR" prescriptions for those dives. It cannot be done. Nor can it be done for a lot of other types of overhead diving unless you have an unlimited budget, which by defintiion, recreational divers do not possess.
Spearfishing in most cases is yet another example. Spearfishing in the FredT case is DEFINITELY an example, but you don't have to be anywhere near that extreme to be unable to meet their definition. There's no way you can spearfish "DIR" the way
I spearfish, and I definitely am not up to the "Helldiver's" methods - nor would I attempt what they do. IMHO, they're certifyable and I'm not talking about their diving cards!
DIR as a system is fine for those who decide to use it. However, the statistics are
not in regarding whether or not it is "safer" or "better" as a dive system. It is
different, but statistically, the claims that are often made for it simply do not hold up under examination.
Among other things, there are very, very few fatalities annually in this sport. In fact, all things considered, its FAR safer to go diving than it is to go skiing, and you're FAR more likely to cap yourself driving to the boat than while actually diving from it.
This low incidence of trouble in the first place makes it almost
impossible to quantify safety advantages.
What may be able to be said is that it makes diving more "comfortable", but again, by who's definition? By the person who adopts the system? Ok. But that's pretty damn subjective, is it not?