It was a lightweight mower with a fibreglass body and an aluminum engine that rode on a cushion of air provided by the rotating blade. I worked at a country club golf course (probably one big reason I'll never be a Republican) and we used it to trim around the water hazards. It would actually hover over the water and cut the grass that grew near the edge in the hazard. It was called a FlyMo. I don't think it ever really caught on and I've never seen one since. However a google search says that not only do they still make mowers, they still make the one I used. It's the L400 pictured on their website.

http://www.flymo.com/node229.asp