You might think that you have seen just about every form of traveling underwater, but check out the scuba diving chair. This DIY project requires one to be tethered to a boat on the surface, hanging on for a ride. Hopefully there are enough safety features built in so that you won’t accidentally end up as some form of propeller fodder. Of course, it won’t help you develop any muscles in the long run since you remain rather sedentary, being dragged around underwater like a maharaja, but at least it is unique.