Sea state scale
The Douglas scale, devised in the 1920s, is used to describe sea state in forecasting and reporting: 0 Glassy calm 0 to 0.1m Rippled calm 0.1 to 0.5m Smooth 0.5 to 1.25m Slight 1.25 to 2.5m Moderate 2.5 to 4m Rough 4 to 6m Very Rough 6 to 9m High 9 to 14m Very High More than 14m Phenomenal
Phenomenal seas might occur two or three times in a winter, off Cornwall, the west of Ireland or Scotland, and in the northern North Sea. The highest recorded wave off the Irish coast was one of 25m, at the Kinsale Field gas rigs in February 2014.
This photo was taken from the bridge of RMS Carinthia by John Shepherd, a Cunard officer, in 1965, on passage from Greenock to Halifax, Nova Scotia. ‘Given that Carinthia’s bridge was 23m (75ft) above the waterline, and these mammoth swells are still...