Why not think about diving as that "second career"? I had been diving recreationally for a number of years and retired in a warm southern clime with water everywhere. What better job can you have, when money isn't the only objective, than being on a dive boat every day as DM/mate/guide? (No, I don't instruct because I have better things to do in my golden years than spend my life on my knees in a pool that is 10 degrees colder than the ocean.)
In Bonaire a couple years ago I met a couple in their mid-80's that required major assistance getting on and off the boat, not to mention that they had to put their equipment on and take it off in the water. But man, once down they were awesome. At 70'-80' this lady would be laying on her side looking at the wall, gradually moving along, and you thought she was asleep! No fin movement, no air bubbles to speak of, literally stationary depth +/- 1', arms folded, was she dead? I hope someday I can dive like that!
Now that it's becoming well known that physiologically older divers in reasonable physical condition are not at particular risk compared with younger folks, assuming medications are also appropriate, if it's going to happen anyway I can't think of a better place to have that "final feeling" than underwater.
If I live to be 100, I hope to be diving at 100.
