As waves move further from their source, the interval between waves becomes longer. A large swell with long intervals is not as destructive as a smaller swells with short intervals. The worse scenario involves Tropical Cyclones, when a cyclone moves towards the shoreline another element is often added. A tidal surge. The severe low pressure in the centre of a Cyclone causes a bulge in the ocean.
Tides can be several feet higher than normal as the centre of the cyclone passes over the coastline.
In Australia, destructive seas can affect almost any coastal area. The most vulnerable areas are the eastern coasts. The southern coast of Australia is used to huge seas and nature has adjusted accordingly. On the East Coast however, truly massive seas may only occur once every few decades. Most are associated with Tropical Cyclones or East Coast lows.