As an operator you can require any thing you like of your divers/customers. Having said that, I am an active instructor, a licensed 100 ton Master, and contract with a dive operator here in FL. I am 67 years old, have been diving since 1958, weigh 163 pounds and display a six pack. I primarily work as instructor and dive master aboard our charter boat. We see every kind of diver you can imagine, and we closely evaluate every diver before they enter the water. All of our team are trained as first responders, and we have all the life support equipment aboard required for dive operations.
The key to any viable operation is making the divers/ customers aware of the risks associated with the diving activity, and having them acknowledge that risk. At that point if they choose to proceed they are assuming the risk. That is not to say we do not expect minimum performance standards, and during or after the first dive we have pulled the ticket of individuals due to safety concerns. Requiring divers to provide a medical certificate to me seems excessive, and is no guarantee that an individual will not have a medical issue at any time. What worries me more than anything
are expirence issues, a person who has not been diving in several years to me is more of a risk that a robust guy or rubinisque gal who has been diving on a regular basis, and who demonstrates general competence and confidence.
I guess what we do on a daily basis is risky business, if we recognize that fact I believe we can be successful. Just my opinion......