I only carried two cards with me when diving - my Advanced Open Water, and my Nitrox Cert card in a neoprene holder I put around my neck and stuck in my exposure suit.

AOW was to show that I have training past 60' plus night diving experience and Nitrox was to show that I could blow mixed gas without killing myself. Anything else wasn't nessecary for the types of diving I did for fun.

I never carried my DM or OWSI card unless I was working - I didn't want the crew and/or other divers looking to me for the answer during the dives in an emergency situation. This was something that was drilled into me from my CD during the liability lecures during DM and OSWI courses.

There's a bunch of 'old wives tales' (which probably have some grain of truth to them) where Instructors who were not in a working capacity had been sued when a diving accident occured because there was a "reasonable expection" that the diver who died "may" have been saved if the Instructor unrelated to the charter company had done something different. Another story that was related to me was that a Instructor was sued when a diver died because that Instructor (who was not on the charter crew) opted to not go on the dive that day and was sleeping in their bunk. There were quite a few more, but those two have stuck with me over the years.

None of this is to say that I wouldn't assist during an emergency. I had the unfortunate chance to put this to the test during a class session at Casino Point, Catalina. We were running the night diving portion of an Advanced Class, and a Sports Chalet group was already in the water while we were gearing up. Those clowns (Sports Chalet) used to really push the PADI rules for OWSI ratios. They would take the 1:8 Instructor/Students and then slam two classes together and have the instructors work without DMs. 1:8 is hard enough in the tropics with little equipment and great vis. Out at Catalina with the exposure suits and lower vis, 2:16 is a recipe for cloud-outs and lost students. Anyway, on the night I was talking about, one of their students had a panic attack and bolted to the surface. She didn't ditch her weights (was grossly overweighted), her BCD was either leaking air or she didn/couldn't fill it, and she was trapped in the surface kelp and was struggling to keep her mouth above water and was swallowing some. To make a long story short: we called EMS, my DM and I fought through the kelp to her and brought her to the rocks/entry steps. Our students pulled her out, secured her gear while we exited, we put her on our own DAN Oxygen kit (which SportsChalet did not want to reimburse for until we threated to call PADI and report their teaching methods) stayed with her and watched her for signs of choaking/loss of breathing until EMS got there (just a few more minutes). The Sports Chalet Instructors didn't even know she was missing until after they finished their dive (~30 mintues or so after she was taken away).

Liability concerns are what ultimatly lead me to begin the practice of solo diving when I wasn't teaching/working if one of my very trusted dive buddies (DMs who I met in my OW class) wasn't around. I always took a redundant air system - Spare Air above 40 feet, Pony bottle below. It was the only way I could truly relax.

Sorry for the long post, but I thought I should give some backing for why I never carried my rolodex of C-Cards.

You can get them from your college's reslife office. Warren res life has them sitting on a desk in the front.