Figure 2: (a) Wave “groups” on a diagram (a) for 6, 5 s interwave. This is the sea surface elevation recorded at any specific station over a time period of 45 seconds. (b) On an diagram, the “groups” are much less prominent, that is, an observer looking at the sea surface over a distance of 500 m at any specific moment in time would hardly be able to discern groups. Blue line: dominant component wave; black lines: subordinate component waves; red line: resultant interwave.