It looked interesting, so I bought one.And it's the most amazing watertoy i've ever seen !!. The ad doesn't explain exactly what this thing does, It somehow converts its buoyancy into forward thrust. It will go probably thirty feet in the water by just holding it down with your foot and letting it go. It works so well.You would think it has a motor propelling it. I'm going to buy a couple more and give them away as gifts.They are very reasonably priced.