Mary paired her relaxed look with a pair of sunglasses as she smiled happily on deck, alongside fellow crew members including her husband.
The Big Boat Challenge is spuiked as one of Sydney’s most spectacular sporting and harbour fixtures.
For the last 24 years it has marked the start of the Rolex Sydney to Hobart Yacht Race.
In recent years Wild Oats XI has all but made the event its own – being undefeated since 2010.
However, this year’s event did not see the yacht claim first prize.
Instead, Black Jack beat its supermaxi rival to end its seven-year domination.
The Big Boat Challenge started off Point Piper at 12.30pm before sailing the harbour, finishing off at Sydney Opera House.
Princess Mary is back in Australia to spend Christmas at her hometown in Tasmania.
The news was confirmed in a statement by the Danish Royal Court, titled ‘The Royal’s Family Christmas 2017.’
'The Crown Prince Couple travel together with their four children, TRH Prince Christian, Princess Isabella, Prince Vincent and Princess Josephine, to Australia and celebrate Christmas with the family of HRH The Crown Princess,' the statement said.