Newcastle Ports Corporation spokesman Keith Powell told Bloomberg early this morning the swell was around the 3-metre mark, down from 5m yesterday.
He said the conditions had eased but ship movements in and out of the port were still restricted.
Several towns on the coast hit by flash flooding have been declared a disaster zone.
Reported by AFP, NSW Emergency Services Minister Steve Whan said 450 millimetres of rain fell on Coffs Harbour in just 24 hours.
The state’s weather bureau has issued more flood warnings for several towns but expects the trough to blame will weaken later on Thursday, causing the rain to ease off.
Less than a month ago the Dalyrymple Bay Coal Terminal in Queensland was disrupted by rough groundswells caused by Cyclone Hamish.