Some canoes are called kayaks. When exactly a canoe can be called a kayak is difficult to determine though, and often arbitrary. Internationally, the term canoeing is used as a generic term for both forms though the terms “paddle sports” or “canoe/kayak” are also used. In North America, however, ‘canoeing’ usually refers only to canoes, as opposed to both canoes and kayaks. Paddling a kayak is also referred to as kayaking. In modern canoe sport, canoes and kayaks are classified together, although these watercraft have different designs, and historical uses. Both canoes and kayaks may be closed-decked. Other than by the minimum competition specifications (typically length and width (beam) and seating arrangement it is difficult to differentiate most competition canoes from the equivalent competition kayaks. The most common difference is that competition kayaks are always seated and paddled with a double-bladed paddle, and competition canoes are generally kneeled and paddled with a single-bladed paddle. Exceptions include Canoe Marathon (in both European and American competitive forms) and sprint (high kneeling position). The most traditional and early canoes did not have seats, the paddlers merely knelt on the bottom of the boat. Recreational canoes and kayaks employ seats and whitewater rodeo and surf variants increasingly employ the use of ‘saddles’ to give greater boat control under extreme conditions.
Reference: Wikipedia Canoeing