Both, IMO.
I'd like to know the reasoning of the dive op since they are the ones imposing the rule. But from your perspective, expand on that and explain how it makes the diver safer and how it makes the dive op safer. If they are dipping the regs in a solution to kill viruses then there will be no covid on them when the diver gets them back. And if there is covid on them when the worker rinses, they wash their hands after rinsing regs.