A billionaire-owned superyacht that was denied entry to New Zealand and instead travelled to Fiji had Covid-19 onboard.

The 85m-long pleasure craft Bold received Ministry of Health approval to enter New Zealand in mid-February, but had been sheltering at Minerva Reef south of Tonga and Fiji due to bad weather.

Instead the superyacht had diverted to Fiji, saying it had been ultimately denied entry to New Zealand because Immigration NZ considered its crew of more than 20 too big a bubble.

Now it has been revealed when it arrived in Fiji on March 6, a crew member returned a positive test for Covid-19.

The superyacht was granted entry through the country's special "Blue Lanes" quarantine programme, designed for yacht arrivals.

Upon arrival a 44-year-old male crew member tested positive for Covid-19 during routine testing as part of the mandated 14-day quarantine on board the vessel.

Fijian health officials said it was a "weak positive" test result, indicating there was "little viral material in the sample".

Non-infectious fragments of the virus can remain detectable, and cause a positive test result long after the infection has passed, and even after previous negative test results, a statement said.

The person also had no symptoms and had tested negative during pre-departure testing in Port Moresby, Papua New Guinea - Bold's last port of call.

Consequently health officials considered it a "historical case of Covid-19".

However, he was still transferred from the vessel and into an isolation ward at Lautoka Hospital.

Fiji Acting Permanent Secretary at Ministry of Health and Medical Services James Fong confirmed to the Herald the man was on the superyacht Bold.

They'd been told the vessel had "a difficult time" finding a port, after New Zealand rejected it.

"We have quite a large quarantine port which makes it a lot easier. They will stay on the vessel for their 14-day quarantine period," Fong said.

"It is a weak infection and from some time ago, so we are not too concerned about it."

The crew would also need to return at least two negative test results before they would be released to enter Fiji.

Fijian health authorities said the yacht did not stop at any other island in Fiji before arriving at the quarantine mooring at Denarau.

This was the first positive case on a yacht arriving through the Blue Lanes initiative, with 107 yachts having arrived since last year.

The Herald has reached out to the vessel's Captain Todd Leech, but has not received a reply.

The superyacht is owned by billionaire German industrialist and superyacht builder Guido Krass, who is currently also on board.

The superyacht had been approved entry to New Zealand under a rule requiring they spend at least $50,000 on refit work.

As the crew had been at sea for more than 20 days the crew would have only needed to quarantine 48 hours. All those on board would also need to have tested negative for Covid-19.

A Ministry of Health spokeswoman said as Bold was not due to enter New Zealand it was "not appropriate" to comment on the current situation.

"New Zealand has effective processes for any crew wishing to disembark foreign vessels which includes establishing how long the vessel has been at sea and testing of all crew members before they enter the community," she said.

As of last week, 54 foreign vessels have been granted an exemption for the purposes of refit or repair, and nine vessels for delivery to a business.

Around 30 of those were "superyachts" - over 24 metres in length - of which 20 were in local waters.

Captain Todd Leech told RNZ on Tuesday Immigration NZ rules around crew numbers meant they would have needed to let go one-third of the vessel's crew to enter the country.

The superyacht now plans to head to Australia, meaning New Zealand companies miss out on refit work understood to be worth $750,000.

Immigration NZ National Border Manager Peter Elms said Bold had requested 23 crew be granted visas as "marine crew", but they'd determined seven crew members with predominately passenger-facing roles did not meet the criteria of being required for the operation of bringing the ship to New Zealand.

"It is the ship owner's responsibility to ensure they fully understand the immigration process, their legal obligations and allow sufficient time to secure all of the necessary approvals before seeking to enter New Zealand," Elms said.

"Anyone wanting to come to New Zealand must make sure they have the appropriate immigration approval before making any plans or beginning their journey."

Bold was built in 2019 by Fremantle superyacht builders SilverYachts, founded by Krass in 2005.

The vessels' naval-like exterior belies its luxurious interior. A massive open-plan entertaining area, known as The Loft, features floor-to-ceiling windows, two artificial fireplaces, sit-down dining for 16 and a movie screen.

An adjoining winter garden, with glass walls that open up, looks down on an expansive aft deck where guests can play basketball or take off for sightseeing on Bold's helicopter.

The helicopter locker doubles as a dance floor for 200, complete with LED lights, a smoke machine and massive speakers.

The toy locker stern door opens up to a beach club with sun loungers, and a floating dock for kayaks, wakeboards, kiteboards, two double jet skis, surfboards, three fast tenders and 12 sets of scuba diving gear.

Bold can accommodate 16 guests and 21 crew with the massive owner's suite featuring his and her bathrooms, including a full-length bath.

Multiple outdoor decks include two outdoor cinemas, an outdoor bar, a jacuzzi and a teppanyaki barbecue area. While in New Zealand Bold was to have repairs and maintenance done, thought to be worth millions of dollars.