Rough seas are battering the central coast, smothering roads with seaweed and debris. 

Wellington's Moa Point Road all the way out to the airport is closed off as huge swells smash up over the road, and the high tides and big swells are blocking parts of State Highway One in Kaikoura.

Police ask motorists to find another way down the east coast of the upper South Island until they can assure its safe.

The heavy swells churning up the Cook Strait have resulted in further disruption for ferry passengers.

Interislander has decided to make its 2.45 Aratere sailing from Wellington freight only.

This as heavy swells get stronger, exceeding the safe passenger operating limits.

Interislander says passengers and their vehicles will be transferred to the Arahura sailing at 6.30 tonight.

Two sailings this morning had to be cancelled because of the conditions.