For a handful of the fleet, this year's Sydney to Hobart is only a warm-up.

Eight boats are sailing the 2024 Hobart as qualification for the Melbourne Osaka Cup - a 5500 nautical mile epic almost nine times longer than the race that starts in Sydney Harbour on Boxing Day.

Among those involved is Annette Hesselmans who, alongside her husband Gerard Snijders, was aboard one of 16 two-handers that completed the last Osaka Cup in 2018.

With a time of just less than 38 days and 11 hours, the pair's boat Red Jacket crossed the line seventh - some 10 days ahead of the last finisher.

There's the small matter of first sailing 628nm to Hobart, but Hesselmans will be back to contest the Osaka Cup again from March 9, this time alongside daughter Sophie Snijders in new vessel Fika.

The pair sailed Red Jacket back together after the last race, managing to only have one argument for the whole journey.

"As a mother and daughter team, it's incredibly special to sail with a family member," Hesselmans said.

"It's almost intuitive sailing together."

While the Sydney-Hobart throws tough conditions at its fleet in the treacherous Bass Strait and foggy Tasmanian coast, the Osaka Cup - one of few south-north long-distance off-shore races - comes with its own challenges.

The conditions should be more predictable as the fleet navigates trade winds, and areas around the equator where the wind stops altogether.

Those periods of calm, when the ocean stretches out like a mirror, are the toughest.

"When the boat's moving and it's moving in the right direction, you feel fantastic," Hesselmans said.

"The calms are more testing because you're just not making any progress, you're totally at the mercy of the conditions.

"When we had no wind or it got quite strong and you're not heading towards Japan, it can just be soul-destroying."

The sheer length is another stumbling block; provided headwinds aren't too intense, Fika should complete the Hobart in four days but will take 35 or 36 to reach Osaka.

And more distance means more chances for things to go wrong.

A cyclone off Queensland forced half of the fleet back to shore in Brisbane during the 2018 edition of the race.

"That second start was almost more challenging than the first start," Hesselmans said.

"You're thinking, 'Oh my goodness, our next destination is Japan. We've got another four and a half thousand miles to go'."

Land is never far away during the Sydney-Hobart, but there'll be times en route to Osaka that Hesselmans and Snijders will feel completely alone.

Once they leave Wilsons Promontory behind in Victoria, the next stretch of shoreline they'll see will be the mountains of Papua New Guinea's Bougainville Island springing from the Solomon Sea.

They'll catch sight of Micronesia up through the Pacific, but won't see land again until Japan.

Fika won't struggle for company, though.

Last time, sharks and dolphins passed Hesselmans' boat, and a booby bird perched aboard for a couple of days.

It was likely looking for meat, but Hesselmans had mostly adopted a vegetarian diet; eggs and hard cheeses will be staples again this time alongside flatbread and yoghurt made on the boat.

"The bird definitely chose the wrong boat," she said.

The majesty of the sea will help Hesselmans and Snijders keep going.

Hesselmans rejoiced in taking the dawn watch last time. Over the Mariana Trench, the water shone magenta as the sun rose.

"That's what I love about offshore sailing and offshore racing, the beauty of the ocean and its changing moods," Hesselmans said.

"It was an incredible race, that first few days, you're just full of self doubt and wondering whether you're going to manage it but there's a sense of relief getting to the start, then you just start to fall into a rhythm."