The Met Service has extended its Yellow Level Hazardous Seas Alert.
The Alert was due to end on Friday, but will instead remain in effect until Monday.
The TTMS says wave heights up to 3.5m have been observed along exposed coastal and offshore areas.
It adds that relatively strong winds are forecast to persist over the weekend into early next week.
There remains an increased risk of strong rip currents which can be life-threatening, even for experienced swimmers.
Agitated seas are likely to be particularly perilous for offshore activities.
This includes fishing and other small craft marine interests.
The TTMS says due to the presence of spring tides, conditions at seawalls along affected coastlines can be exacerbated, especially at high tide.