My wife and I were certified a year ago when she was 54 and I was 58. We love diving so much we were initially sad we waited so late in life to start. We expected we would be the oldest divers where ever we went on dive trips. We've been on about 50 ocean dives in the last year and we have never been the oldest on the boat. On a recent trip we were actually the youngest by several years on some days!
Friends have asked us about increased risks at our age....my wife replied before I could, "if we die we die doing what we love". As a physician I realize that despite the fact that we are both in great health that we are at additional risk to younger folks but the reality is we never know when our number is up. I have a patient who had a major heart attack at age 31. He was a marathon runner and had perfect blood pressure and lipids before his MI. His cath was normal except for one congenitally compromised artery. You never know.
I was 33 when I took my first dive. Of course I wish I started earlier. I think everybody does. Even after 1500+ dives, I still wish I had started earlier. You just accept the elevated risk and do everything you can to mitigate it. While almost all who die of a cardiac event are older, not many older divers have cardiac events. I've had the pleasure of diving with some Hall of Fames divers who older than I. I figure if they can keep doing it, so can I. While I a fit for my age, I am not the same diver I was back in the day. I gave up instructing about 6-7 years ago. One minor reason was the knowledge I couldn't do some of the save scenarios I once did. A couple of years ago in Komodo, a diver needed help. I was about to take off to help when the DM tapped me on the shoulder and told me to stay put. He then took off faster than I ever could. I let him. We are now into very low stress diving.
So, everyone keep yourself in shape, get yourself checked (stress EKG), stay shallow and always use sunscreen.