A DO does not have to certify anybody is fit to dive. A DO has to have belief that a member is fit to dive. The best way is to inform the DO is a self certificate. If you can not certify yourself fit you need to see a medical refferee. if the medical refferee puts a restriction on the diving the DO needs to know what that restriction is. A DO does not need to know the reason only the restriction. If an individual diver wants to discuss his medical condition that is his choice.