Kayaking is the use of a kayak for sport or recreation. Whitewater kayaking involves taking a kayak down rapids.
Sea kayaking involves taking kayaks out on to the ocean or other flatwater. Sea kayaking can be thought of as hiking or backpacking over water, with the similar goal of sight-seeing and touring.
Kayaks are propelled by hand-held paddles.
See also
More links
http://www.paddlepedia.com is a online wiki focused on documenting and publishing paddling.