Having run a charter boat in the Med on a part-time basis for several years, I will simply turn to that full-time very soon. You don't have to be young and fit as a Gazelle to run such a business. Gentle sailing with guests ranging in age from teenagers to people almost as old as myself is a wonderful way to spend your time.
I would suggest that doing something on a more or less daily basis will be far better for you than simply retiring and doing nothing or very little. I have seen people retire and do nothing and they simply fade away in a few years and drop dead with boredom. Think positively, start again with something new if neccessary. But do keep busy and always have a reason to get up in the morning.