Passengers on the Cook Strait Interislander ferry, which was crossing a point near the quake epicentre when it struck yesterday, were alarmed by the shaking felt on the ship.
Richard Osmaston, of St Arnaud in the Nelson region, who was travelling towards Picton on the ferry, said a noticeable vibration was felt.
An Interislander spokeswoman said the Arahura captain thought at first he had hit something.
''Everyone went quiet, then the captain came on the public announcement system and suggested it was a quake, which he confirmed a few minutes later,'' Osmaston said.
The Aratere ferry, which was tied up alongside the wharf in Wellington, also was aware of the shake.
''We certainly felt it on the ship. It was a big rumble, but it didn't do any damage.
''We could see the lights on the motorway flicking back and forward, other than than it was just a rumble but we definitely knew it was a quake.''