Thanks for the replies guys. I share your thoughts also, which is why I want to approach this matter sensitively, whilst at the same time making sure that customers are not taking undue risks. We are located in Little Corn Island, Nicaragua which has nothing more than a basis clinic with a part time nurse. The nearest island which is 8 miles away has a basic hospital, but for any proper medical facilities you need to travel to the nearest mainland port which means a 50 mile boat crossing (boats go twice a week) or a small plane. The best hospitals are in the capital, Managua which is an hour plane ride from our neighbouring island. The nearest chamber is 6-8 hours by boat, but there is no boat service to get there so it means renting a boat at a cost of around $1500, in cash (we have no bank or ATM here either!!)
We're not the only location with such challenges, and we have a number of divers over 50 who are just fine, as most of you are also I'm sure. The customer who had problems yesterday was not overweight, does not smoke, but as it turns out was feeling sick and had not drunk any water, both of which he failed to tell us. It is this kind of customer I want to protect, those that are not experienced and don't necessarily know what they are letting themselves in for.
When I have seen potential divers who are clearly in high risk categories then I have always exercised caution, and will continue to do so.
I guess the feedback here is that asking for a medical would be over the top, although to be honest if we lost a few customers to save a life then that's fine by me. It may be more appropriate though to just ask for proof of insurance for over 50s. I will continue to look at options, but thanks for your honest opinions!