Really funny you mention that.heh I retired from that job in 86, got tired of rescuing bath tub divers from southern cal that had no business diving in open water
After my first couple of group boat-dives out at the Channel Islands, I learned to never ever show them anything above my Advanced card (like the Rescue or DiveMaster card), because the boat operators would already know which divers were the liabilities, and pair up any prepared/trained divers like myself with them. After my first two dives being underwater rescue missions of the spodes I'd been paired up with who either didn't know their gear or weren't at all comfortable in open water, I started leaving the DiveMaster card at home.
I learned to dive in Illinois in a limestone quarry that had 0-10' vis, so I was always baffled when the 10-30' vis at the northern Channel Islands would mess with some of the divers out here. I don't know how the hell they ever got past the underwater navigation requirements.