Was she in fact coming off a boat? As otherwise there is no reason for her to have a life preserver at all. And due to her age, it could well have been a heart attack or stroke. The DH story says she 'went for a swim', which to me means she was just at the beach, not on a boat. Regardless, a very sad thing for her family and friends. It's a cautionary tale to all of us, tomorrow is guaranteed to no one.