True whitewater boats are quite different from recreational or sea kayaks. They have a very different purpose – to avoid obstacles instead of covering distance. As such, they turn easily but are hard to make go straight. And while you can get inflatable kayaks and even Sit-On-Tops designed for whitewater, but I’m going to stick to your basic hardshell, plastic kayaks for this one. They generally range from 6′-9′ in length, have a cockpit with outfitting that allows a tight fit and a solid sprayskirt. Most boats are open inside, without bulkheads (float bags are used to help keep them from sinking), but often with foam pillars to provide strength and rigidity.
Paddling on the river can be broken into two general styles: playboating and river running. Playboating is about doing tricks – surfing waves, cartwheeling the boat, even doing flips and twists in the air. It can be done anywhere on the river, but often people will spend an entire day in one spot playing on one river feature (it’s like the terrain park for snow/skate boards). River running is about going down river, through rapids, from point A to point B. It’s downhill. The spectrum of boats goes from dedicated playboats to creekboats for steep river running, with various styles in between that aim to do both to some degree.
Playboats are on the small end. Modern playboats are under 6′, with a wide, flat bottom. They are stubby with relatively fat ends (older playboats had thin, slicey ends). The flat bottom (known as a planing hull) allows the boat to rise on top of the water when surfing waves (just like a surfboard), which makes them faster and more responsive. The big ends allows them to perform aerial maneuvers where their buoyancy actually makes them pop out of the water entirely. While great for tricks, these boats are less stable, get pushed around by the water more, and are far slower than longer whitewater boats.
On the opposite end are creekboats. These are designed to handle the most difficult whitewater. They are around 8′ in length, have a fair amount of rocker (banana shape), and normally softer edges than playboats. They are more forgiving and stable, faster, and resurface better after big drops. Some have a semi-planing hull (not quite as flat as playboats), but many have a semi-displacement hull (more rounded). A little discussion of the differences in performance based on hull shape can be found in our Jackson Hero review.
But creekboats are often too stable and forgiving, making paddling easier rivers not so much fun. But playboats are often too playful, hard to manage and paddle downstream. So a large number of boats fit in between the two, and we call these river runners. Some are closer to playboats in design while others are quite similar to creekboats. Most river runners are going to have a fairly flat bottom but softer edges than playboats. The larger river runners will have as much volume as a creekboat but with less rocker they are a little faster and often more responsive. Most paddlers find it easiest to learn the sport in a river runner and we use higher volume river runners for our classes (Jackson Zen Review).
Regardless of boat type, each manufacturer has their own take on the outfitting for their boats. Everyone has their own preference, but what you are looking for is a boat that fits snug and gives you the support and control you need to maneuver the boat on the river. Whitewater boats come in different sizes to fit different folks; size up if you want more stability, size down if you want more playing.
Ultimately most whitewater kayakers end up with at least two boats, often more. One creeker/river runner for doing more challenging downriver runs; and one playboat/small river runner for easier stuff when they want to goof around. Like all other types of kayaking, the key is to have something so you can get out on the water and enjoy yourself.