captain
Contributor
I carry two of everything when I solo, inclulding a spare mask.
Recently I decided to start wearing a back-up compass, too.
My primary compass failed on my first dive with a back-up compass.
Two masks
Two sets of 1st and 2nd stages
Two tanks
Two bottom timers
Two compasses
Two cutting devices
Two floation devices (BC & dry suit)
Two depth gauges
Two lights
Two halves of a brain (most of the time)
WOW, the submersible dive shop.