Answer:
A Sea kayak differs from a lake or river kayak in that it is longer, therefore faster. Also the hull width is generally narrower than a lake kayak, making them less stable but in turn faster.
Sea Kayaks are designed for longer distance travel on the ocean or lakes. The longer the kayak the faster the boat. Sea Kayaks generally range in length from 14-18 feet in length.
Lake kayaks are designed for shorter trips, generally they are wider - this causes them to be more stable. They range in length from 9-14 feet.
River Kayaks are shorter, this causes them to be slower but more maneuverable so that they can avoid rocks and holes. There are two main types of river kayaks, playboats and creek boats. Playboats used on rivers and are the preferred boat to do tricks in. They are shorter than creek boats and have a flat bottom. Creek boats are best in narrow creeks with a lot of rocks. They have round bottoms in order to slide off the rocks.