For OC: Primary-Perdix AI on left wrist, Petrel and watch on right wrist. Tables/slate in pocket.
For CC: ISC controller and secondary Petrel on left wrist, Hardwired Predator and watch on right wrist.
There are occasions when I’ll dive CC and OC on the same day, most likely I’ll dive CCR during the day, then dive OC for a blackwater drift dive that night. In those instances I rely on my Petrel as my OC primary, (it’s monitored my previous dives), and the Perdix becomes my SPG.
I do not do blackwater drifts on CCR for a few reasons: The creatures I’m shooting are almost all tiny and many are not bothered by exhaust bubbles. Depth changes occur frequently which makes proper PO2 monitoring and adjustment problematic. If I’m fortunate enough to find some tiny creature that will allow me to spend a few minutes photographing it, I prefer to concentrate on it and my camera, as opposed to monitoring my displays. Take your eyes off the subject for even a second or two, and there’s a good chance that you’ll never find it again. The local operators that I use for these dives suggest as common courtesy that dives are limited to a maximum of 90 minutes, and average depths are relatively shallow, thus a single cylinder is sufficient for the task at hand.