Parachute was one of the things I thought about when I was developing DragSox. I liked the drag that parachute created but there were two things that I really didn't like about them. One was that my foot was constantly hitting the strap, making it hard to get into the rhythm of the stroke. This is a common complaint. Second is that because the parachute is attached to the waist, it slightly pulls you down, changing your body position. I wanted a device that would give benefits of the drag with out the drawbacks I listed. I wanted something that I could move freely in and keep my natural body position. DragSox gives all of these.
A few months ago, I tried modifying a parachute to attach to the ankles. It was better, the body position was not as affected but I still didn't like it as much as DragSox. With a parachute, you're dragging something behind you, like an anchor. DragSox, on the other hand, feels like they are a part of your body. They add drag, but in a way that's natural.