Many of us will make it to 84, and will need a handgun during our daily rounds and for home defense, a handgun to be carried at all times because at 84 one can become a vulnerable target.
At this age a reliable, easy to operate, small handgun is paramount, which unfortunately rules out semi-autos (ie must rack the slide, jams a problem, etc.) and larger-bore handguns such as 44 spl and 45 ACP.
My choice would be a small no-snag J-frame 38 spl S&W 438 with cowboy load ammo, i.e. Black Hills 158gr RNL, an old time effective, yet recoil friendly cartridge.
For 20 years the sea was my home, always recall the sun going down, and my trusty friend, a 1911 pistol, strapped to my side.