After all, the ship wasn't meant to be in Tasmania in the first place - her family had booked a cruise to New Zealand, a "Kiwi Adventure" 14-day trip for the 16 of them, all from Wollongong.

But the Pacific Adventure ship had been refused entry to New Zealand because of an "invasive species" which the cruise line had failed to clean off the ship's hull, understood to be mussels.

First, stops in Auckland and the Bay of Islands were cancelled but worse was to come.

After attempts to clean the hull failed, notes were left outside cabins informing people the "itinerary" had changed again - they would not be stopping in the Shaky Isles at all, with Dunedin, the Fiordland and two other stops scrapped.

The new itinerary had them going to Tasmania and then Eden on the NSW Far South Coast.

"We were devastated," Ms Cockburn, 49, told ACM's Illawarra Mercury after a few hours in Hobart - a lovely city but hardly the Kiwi holiday they had in mind when they booked with fares about $8800 for a couple.

"It's gone, actually, from an international cruise to a domestic."

Now they face a battle with P&O which refused to give a proper refund, instead offering money to spend on board and discounts on future cruises - cruises this family will "never again" be taking.

This was later changed to a 50 per cent refund, but that's not good enough for Ms Cockburn.

"When they [offered the discount] my sister and I hit the roof," she said.

"We went down, we 'did a Karen' and we demanded to see the manager. Then we had to wait two days to see the manager on board the ship.

"When we finally got to see the customer relations manager, they said 'we want your feedback'.

"I said, there's no point in labouring it. We want a full refund and monetary compensation. There's nothing else. Nothing more to discuss. Nothing more to negotiate."

By Wednesday Ms Cockburn and her family, along with thousands of other passengers, had been on board the ship some dubbed the "cruise to nowhere" for almost nine days with no stops - spending their on-board credit on essentials such as bottled water and wi-fi.

Ms Cockburn is particularly critical of P&O because they had contacted her on November 16, several days before the ship was to depart Sydney, informing her of the need to clean the hull. But it wasn't done.

"The ship sat at dock in Sydney for two days after it returned from another cruise - why did they not just clean it?"

This isn't the first time for a P&O cruise - a similar cruise on its Pacific Explorer was denied entry to Fiordland National Park in May.

Several other cruise ships have had similar troubles in recent years as New Zealand maintains a tough biosecurity regime for its pristine waters. The demands are well known.

Ms Cockburn thought the offer of a discount cruise and on-board credit was "an insult" given the expense, inconvenience and disappointment involved.

There are many more expenses involved than just the fare - there's tours, transfers to Sydney, annual leave from work wasted, and more.

Five of her family had got new passports ($350 each) for the trip, including her 86-year-old mother-in-law who had never been to another country. She still hasn't.

Ms Cockburn is a Kiwi herself and she had organised visits or tours with NZ family while in port - these had to be cancelled, with more money being lost on bookings.

The Mercury asked P&O whether there should be a full refund given.

"P&O Cruises Australia was hopeful it could get the necessary hull cleaning done off the Bay Of Plenty however unexpected changes in the weather forecast made it too dangerous for divers," a spokeswoman said.

"This meant we were unable to get clearance to enter NZ, and we apologise to our guests for the change in itinerary.

"Guests on this 13-day voyage on Pacific Adventure have received $300 on board credit per person, as well as the 50 per cent refund off the cruise fare paid."

Ms Cockburn and her family are unlikely to leave it there and said they were looking at potential legal action.