I thought these Flyboard water jet boots were pretty cool:
The Flyboard is a water sports piece of equipment which mounts to your feet like a wakeboard and causes the water that is flowing out of the jet ski to propulsion you underwater and in the air; wherever you desire to ride. The flyboard is all about balance and when you master the distribution of your body weight on the flyboard you'll be able to control and experience this amazing flying water sport! Usually after about 25 minutes you can already move underwater like a dolphin and challenge the gravity like super hero!fly board
The nozzles under your feet puts 100% of the propulsion from the waverunner and allows movement by tilting your feet and tilting the Flyboard. The flyboard is very intuitive: similar to learning to ride a bike, waterski, surfing, skating, air chair, wakeboard or any other activity that requires a little balance. Find your balance and you will be flying in the air like a bird or swimming through the water like a fish! For most people it takes about 5 to 20 minutes to learn the basics of flyboarding with an instructor.
Golden Age writer Francis Flagg described something pretty similar in his 1930 classic An Adventure in Time, published in Science Wonder Stories. He called them air-shoes:
Manuel fastened to my feet the metal, disc-like devices I have before noted. Closer examination revealed
them to be quite broad on the bottom and punctured with
a score of small holes, containing a small compact atomic
motor that compressed the air beneath one and made it
as hard and resilient as rubber. The short metal rod
handed me was hollow, and at either end, like stoppers,
were what appeared to be sensitized plates. The rod was
fastened to the wrist by a flexible strap of metal. Three
keys, red, white and blue, were at the end of the rod nearest the wrist, and there were other devices whose function
I will describe later on.