Though most rafters don't want to be associated with tubers. Tubers are notorious for getting into trouble, getting in over their heads and having no safety equipment. Kayaking is one of the best boats to build your whitewater skills. The boat is light and very reactive, so you'll begin to feel the river. This is important for eventually being able to read the river.
Some people seem to have a natural ability to read water.
It's subtle, but key to avoiding potentially hazards as well as finding good clean paths or lines. Whitewater kayaking offers plenty of excitement and adrenaline. It's different from most sports in that a major part of the sport is in your head. You have to keep your fear in check. The only way to really build your skills is to be on the water, so you just have to get in there and do it.