The obvious 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 for 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...
As opposed to a canoe, sea kayaks are enclosed and can have a rudder and therefore are more appropriate for the ocean. Sea kayaks can also carry enough camping gear for a comfortable stay on offshore islands.