Hard-bitten Sydney to Hobart race regulars have returned to dry land with stories of challenging conditions and some hard luck after more than a quarter of the fleet retired within the first 18 hours.

A full 24 hours into the race, Monaco's Black Jack was leading from fellow supermaxis LawConnect and SHK Scallywag as they battle off the Victorian coast, with a total of 62 boats still racing.

Eighteen boats pulled out on Sunday and a further eight followed on Monday morning as the conditions took a heavy toll.

The most prominent withdrawal on Monday was Alive, which won overall honours in 2018 and was fourth in 2019. The 66-foot Tasmanian yacht suffered hull damage and was heading back to Sydney.

Sailors returning to Sydney said it was heavy seas that caused most problems rather the southerly winds they were pushing into.

"The breeze was 33, 34 knots, which is not that bad," said No Limit crew member Declan Brennan, whose boat retired after one of the crew suffered a dislocated shoulder.

"Its curious, it wasn't angry conditions it was a just a very short, sharp seaway.

"The seaway was so inconsistent we were just bouncing around all over the place.

"This is a 63-foot boat. It just didn't make for a sensible thing to continue on."

South Australian John Willoughby, skipper of Enchantress, at least got nine hours into the race this year, having spent eight days in 2020 sailing from Adelaide to Sydney only to find the race had been cancelled minutes before he arrived.

His 2021 campaign was cut short after some spinnaker halyards came loose and knocked a hole in the mainsail.

It was part of a sequence of adverse events triggered by the boat being briefly plunged into darkness by an electrical fault.

As someone used to dealing with things going "pear-shaped" with a rudder falling off in three races and a mast going overboard in another three, septuagenarian Willoughby was too busy to get panicked.

"Thats what a Sydney Hobart does for you, it gives you the knowledge and the training to be able to get yourself out of any situation," Willoughby told AAP.

"But if we had gone on with that mainsail it would have just torn to pieces."

Tasmania's Cookson 50 Oskana, which won 2013 overall honours as Victoire, retired this year after breaking a headsail foil.

"We couldn't hold a headsail in that track and that was going to make it a really hard race if it's all upwind without a headsail, so we decided to retire, no major damage," Oskana skipper Michael Pritchard said.

"It's the coming down off the waves and landing is what shakes things out of the foils, so unfortunately it blew the foil out."

It was the first time in his four Hobart campaigns Pritchard failed to finish.

"The other Hobarts I've done have been quite a downhill run, this was a bit of a challenge," he said.

Cruising Yacht club of Australia commodore Noel Cornish explained the conditions.

"The southerly at up to 30 knots is not an unusual southerly for this sort of race," said Cornish.

"But the north travelling south current going against that 30-knot southerly is what has caused quite steep seas and that's what has done the damage.

"I think as the day progresses it's due to abate as a southerly front just moves through and moves up the coast."

© AAP 2021

The number of people hospitalised with COVID-19 in NSW has doubled in the past week, as testing numbers continue to plummet despite rising COVID-19 cases.

Some 6324 new infections were diagnosed from more than 97,000 tests on Sunday, with the state also reporting another three deaths.

While the number of new cases dropped by 70, the number of people hospitalised has doubled in the past week.

A total of 521 people are in hospital, 55 of them in intensive care.

Testing numbers also decreased by more than 12,000 compared to the day before.

The number of tests processed each day has plummeted by more than 60,000 over the past four days, as testing sites and laboratories become overwhelmed and wait times blow out.

Adding to the state's coronavirus concerns are hundreds of people receiving falsely negative test results on Christmas Day.

More than 400 people who initially received a negative result on Christmas Day were then notified they had tested positive on Boxing Day.

St Vincent's Hospital in Sydney revealed on Sunday a mistake had led to its pathology department incorrectly telling people they had tested negative on Christmas night.

The incorrect results pertained to people who had been tested on December 22 and 23.

The mistake, attributed to human error, is being investigated as concerns remain about those who took the initial negative result as reassurance to attend events over Christmas.

The revelation came as NSW Health Minister Brad Hazzard revealed the government is considering lifting isolation requirement for health workers exposed to COVID to stem looming staffing shortages.

"I'm certainly in deep conversation over probably the last week... about whether or not it's viable to have staff coming back sooner," he told reporters on Sunday.

They would wear fitted P95 masks and full PPE, Mr Hazzard said.

"If you're erring on the side of caution, it would certainly be an area that you could say probably this would be a safer option than having no staff."

Mr Hazzard also warned everyone in Australia was likely to be infected with the Omicron variant at some stage.

It's highly likely everyone will spend 10 days in isolation in the next two or three years, he said, but noted symptoms appear milder and the current approach to isolation may change.

His comments drew criticism from NSW Labor health spokesman Ryan Park.

"Where's the planning and where's the resources and where's the leadership?" Mr Park said.

More than four in five residents aged between 12 and 15 are fully vaccinated. This increases to 93.5 per cent for people aged 16 and over.

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Marcus Harris looked nervous and unconvincing in the last hour of play on Boxing Day.

But unlike 10 English batsmen and his opening partner David Warner, the embattled Australian has survived.

The left-hander will resume arguably the most important innings of his career on day two of the third Test at the MCG, aiming to repay the enormous faith that the selectors have placed in him.

Harris has made 20, still three runs shy of his highest score so far in this series.

He edged the last ball of the day off Ben Stokes through the slips for four.

Harris will have gone to bed knowing the English will come hard at him and nightwatchman Nathan Lyon on Monday morning.

Australia are 1-61 in reply to England's first innings of 185 and the unusually green MCG pitch is offering plenty for the bowlers.

"We're also bowling on the same pitch that they bowled on," England's Jonny Bairstow said.

"We turn up again in the morning. We've seen the pitch offer plenty throughout the day and ... we've got one end that's potentially open with the nightwatchman.

"We look to put pressure on Harris and the nightwatchman, to get some early inroads."

As is his habit, Warner took the lead at the start of the Australian first innings.

He'd had made 38 from 42 balls before Jimmy Anderson made the crucial breakthrough, having him caught by Zac Crawley in the gully.

After Harris only managed three and 23 in Adelaide's second Test, he looked unlikely to play at home ground on Boxing Day.

But coach Justin Langer and the selectors have stuck with Harris in the hope that they can finally translate solid Sheffield Shield form into consistent Test runs.

Day two will reveal plenty about whether that faith is justified.

© AAP 2021

Supermaxi Black Jack was heading a much reduced Sydney Hobart fleet on Monday morning, after the double whammy of strong winds and high seas forced almost a quarter of the boats to retire.

By 6am (AEDT), 21 of the original 88 starters were no longer racing and the other 67 were hoping for less taxing conditions, after being battered by heavy southerlies through the latter part of Sunday.

By the time Boxing Day on the Australian east coast had finished 18 boats were out of the race and three more joined the list in the early hours of Monday morning,

Sydney boats Oz Design Patrice Six and Philosopher withdrew due to engine issues and internal damage respectively.

Queensland 39-foot yacht Huntress also advised organisers she had retired, but it was not immediately clear why she had pulled out.

While the three supermaxis remained in the race, the big list of casualties on Sunday included the TP52 Gweilo, which was considered one of the main contenders to win overall honours.

Out the front of the fleet, Monaco's Black Jack continued to lead in the battle for line honours.

She was ahead of rival supermaxis LawConnect and SHK Scallywag 100,

The size of her lead was hard to confirm as LawConnect had issues with reporting the boat's exact position.

Victoria's 80-foot Stefan Racing, skippered by race stalwart and co-owner Grant Wharington, was also up among the fleet leaders.

Other boats in the top ten included Tasmania's 2018 overall winner and 66-foot boat Alive, the 62-foot Whisper and TP52s Celestial and Quest.

The 64-foot Sydney based boat Khaleesi was leading the overall standing from the 34-foot White Bay 6 Azzurro, which before the race was considered one of the small boats most likely to challenge for the main handicap prize.

In the new Two-Handed division, Tasmania's Sidewinder was leading that contingent of 15 from Victoria's Maverick.

© AAP 2021