I recently had a dive shop in the keys through up all sort of flags for going to a wreck. Luckily, I was taking an advance class and my instructor had the required medical waiver in his care. I certainly understand an instructor needing it, because you are paying for a course, whereby you conditions might not allow you to meet the standards. However, as a paying diver for a boat, and my dive is my own business (ie. the shop is not planning my dive nor would they ever), my medical condition should fall upon me.
As someone analogied to a pilot, perhaps we should ask to see the physical for the boat Captain prior to signing the hold harmless waiver. What if the Captain has deep seated psyche issues or medical problems. I agree "Show you mine, show me yours".
I don't think I will get very far with that logic, so I am going to ask my Doc to fill out the waiver form for me again and keep a laminated copy in my log and vehicle. This way I am always covered. If the dive shop wants a copy, they can make their own. Pffftt