[renewiltord]

Well, presumably if OP statement were true, recreational diving would involve large numbers of casualties. Casualties in recreational diving are somewhat rare, however, at 2 per million dives.

Tourist dives are even safer since they do not perform advanced dives. Overall, the evidence does not support the view "If you really have only a vague recollection of basic safety checks you shouldn't be diving - seriously."

Most tourists diving have only that and they're not dying in droves.

[bonzini]

Of course, because things very rarely go south, especially to the point of someone dying. But still, spending half an hour reviewing some basic course material is not a huge thing to ask.

[renewiltord]

Yes, it is certainly acceptable to ask for that. Not arguing that.

Merely pointing out that there is no evidence for the assertion as stated.

[bonzini]

I interpreted it as "they don't understand the dangers implicit in diving", i.e. they don't have the right mindset for diving.