Kayaks can broadly be placed into 3 categories: Sea/Touring , Whitewater and Recreational.
Composite Sea Kayak
A Sea kayak or touring kayak is a kayak developed for the sport of paddling on open waters of lakes, bays, and the ocean. Sea kayaks are seaworthy small boats with a covered deck and the ability to incorporate a spraydeck. They trade off the maneuverability of whitewater kayaks for cargo capacity, ease of straight-line paddling, and comfort for long journeys.
Sea kayaks are used around the world for marine (sea) journeys from a few hours to many weeks, as they can accommodate one to three paddlers together with room for camping gear, food, water, and other supplies. A Sea Kayak usually ranges anywhere from 10–18 feet for solo craft, and up to 26 feet for tandem craft. Width may be as little as 21″, and may be up to 36″.
Whitewater Kayak
Whitewater kayaking is the sport of paddling a kayak on a moving body of water, typically a whitewater river. Whitewater kayaking can range from simple, carefree gently moving water, to demanding, dangerous whitewater. River rapids are graded like ski runs according to the difficulty, danger or severity of the rapid. Whitewater grades (or classes) range from I or 1 (the easiest) to VI or 6 (the most difficult/dangerous). Grade/Class I/1 can be described as slightly moving water with ripples but for that reason is not considered ‘Whitewater.’ Grade/Class II/2 can be described as moving water providing some small degree of challenge. Grade/Class VI can be described as extremely severe or almost unrunnable whitewater, considered almost certain death, such as Niagara Falls.
Recreational Kayak
A Recreational Kayak is a type of kayak that is designed for the casual paddler interested in recreational activities on a lake or flatwater stream; they presently make up the largest segment of kayak sales. Compared to other kayaks, recreational kayaks are characterized by having a larger cockpit opening for easy entry and exit and a wider beam (27–30 inches) for more stability on the water and are generally less than twelve feet in length, which makes them slower than a longer boat would be, but lighter, easier to handle in and out of the water, and less expensive. Due to the wider hull, recreational kayaks will not track (maintain a straight line) as well as longer, narrower models. They generally have limited cargo carrying capacity. Using less expensive materials like rotomolded polyethylene and including fewer options helps keep these boats inexpensive.