Meet the Bixpy Jet: a propulsion system that you can attach to your kayak, SUP, or hold in your hand to move over and underwater with less effort. The motor weighs just over 1 kg and can push your kayak over 7MPH.
The Bixpy Jet is about the size of a water bottle and pushes 100 gallons of water per minute. It has a modular design. You can find out more on Kickstarter.