You don't have to be 'old' for this to happen, I have seen overweight young divers laying on their back like a turtle turned over in the shallows, funny to watch, then it becomes serious when the regulator is lost and waves roll in.I had an incident where I stumbled and fell on a shore exit and what "normally" would have been a "piece of cake" was more difficult than I thought to get back up on my feet. It was an eye opener for me.
splutter, splutter cough, help.
A 2nd regulator on a necklace would have saved some of the drama, or even a Air 2, as the main regulator was under him when we helped lift him, and his occy was tucked under his right arm pit, too hard to find.
Old fit and smart.
Not, young fat and dumb.