I have one of those 4 cylinder 1800cc Supercharged Barges with handlebars on it, and it's pretty fun on it's own, I don't think I'd actually want to race it against other things like that on a course, it would be very dangerous they are so fast and powerful. I mostly use the power to propel people up in the air on the Flyboard, and that is a ton of fun. I had Rocky River High School hockey players doing it yesterday and they all had a blast.
Racing Jet Skis was a lot of fun in the WaveBlaster days.