The whitewater kayaker wants a boat that is very easy to maneuver. These boats are much shorter, around 10 feet long. The most incredible thing about sea kayaking is how close you can get to animals. Most wildlife don't fear kayaks, yet. And because kayaks only draw about 3 inches of water you can go practically anywhere there's water.
Sea kayaks are much more stable than whitewater boats.
This makes the learning curve shorter. A novice can immediately participate in the sport. As you get into the sport you'll hear a lot of people talk about the dangers. Sea kayaking can be dangerous. However, most of the danger lies in not using your common sense.