I love using the water aerobics equipment. It always makes me think about this story.
My mother tells me that when my father was a young man, and involved in sports and swim equipment manufacture through his job, that he had a chance to endorse one of those buoyant vests they use now to run and walk suspended in the water.
He laughed and said it would never find a market. I know, I know, it's one of those cautionary tales. He was too interested in athletes. He should have thought about the potential for rehabilitation and the elderly.
Then he might have made a bit of money!