I started at 66 two years ago. I've got almost 100 dives, many of them over 100 feet. I've never wussed out on a dive no matter how high the waves are or how cold the bottom water was except for one time when I tore a calf muscle leaving the boat on the first dive. If the boat captain says we're going out, I'm on the boat and usually the first one off. I've seen a lot of them a lot younger than me puking over the side or complaining about one thing or the other and giving up dives. It's physical and mental conditioning, not age, that are the determining factors.