| As I was taught it, two backups are not necessary when you have ambient light. In fact, it makes sense to look at the dive you're doing, and see whether a backup light will be of any use at all. In 100 feet of viz in tropical sunlight, I can guarantee you that most backup lights are only going to be good for looking in deep holes. I usually don't carry one in the tropics for daytime diving.
On the other hand, I carry my Salvo 21W for every dive -- Not because its presence or absence affects my position, weighting or trim, because it doesn't, but because I've been amazed at how useful it is even in tropical conditions. It brings out color, and heightens the relief to help you find well-camouflaged critters, as well as illuminating holes and overhangs. It is nearly worthless for signalling in clear water in the daytime, though.
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"So, it's a good thing to always do the drills the same way . . . but in real life you need to act the right way, whatever that happens to be." LauNar |