I’ll throw my fins in the ring of this forum discussion. When I went diving in Hawaii with a friend (I had certified her both OW and AOW) we both boarded the boat and showed our cards. This was 2004 so at the time I was just a PADI IDCS. The boat Captain said, "Let’s see, Advanced and...one more than Advanced." I smiled and moved toward my gear to resume set-up. When I go diving I have over 600 cards in my folio to choose from. I can also say that I have been diving in many places that never ask me for a card but have called me out for being an Instructor after the first guided dive because I didn’t need nor ask for assistance. Greg is correct that many dive professionals believe that if they show a recreational card instead of a professional card that they don’t assume any liability. That’s like saying that if I drive Greg’s car instead of mine that I’m not responsible if I wreck it. The facts are simple. If your buddy has an incident then you are responsible as her/his buddy to assist. If you are a dive professional then you may be responsible for filling out an incident report on your buddy’s problem regardless of whether you were teaching or simply diving as their random buddy - check with your agency or in the General Standards, safe money says the report is required for many larger agencies. If there is an incident then the first person they will look to in an investigation is the buddy - and you’ll be required to cooperate with the investigation by showing your certification card(s). Failing to disclose your Instructor status in an investigation could lead to charges of obstruction and regardless of fault, the authorities looking harder at you to try to pin it on you since they now think you have something to hide. Finally, your Dive Instructor Professional Liability Insurance only covers you if you have a proper waiver signed! This means that if you board a boat on holiday and get paired with someone you need to get them to sign a waiver or your insurance is not valid! Read the fine print in the full policy and you’ll see that if your paperwork is incomplete then your policy coverage is void. There is a certified diver waiver (the one for guided dives in most agencies) that your buddy must sign in order for your insurance to cover you. If a boat attempts to hook you up with a random dive buddy then you as an Instructor should protect yourself by getting them to sign a liability release/waiver prior to boarding the boat or you could be personally liable with no professional liability insurance, whether you showed your Instructor card or not. An omission of the facts does not remove your legal, professional, or ethical liability regardless of what any bar room lawyer will tell you. Do some people get intimidated by Instructor cards? Absolutely. Should that concern you? Not really. Just show the correct card and be the best buddy you can be - if you want to. I usually show my Solo Diving Instructor Trainer card and tell the boat, "I do not want a dive buddy, thank you." If they want to give me a buddy then I request payment as a staff member and we then go inside to fill out waivers.