The major difference between sea kayaking and white water kayaking is the ocean. Swells can and do reach rather large sizes, on the order of 10 feet or more. Wind driven rain may fiercely oppose any attempts to paddle against it.
Tidal currents can dramatically slow down or speed up the progress of the boats.
Yet all these risks are worth taking just to experience the breath taking experience of surfing large swells, or ramming through powerful breakers on the way to and from the beach. Islands accessible by kayak offer privacy and solitude not often found by hikers. And sunsets dazzle with their brilliant shades of red.