Four supermaxis were Thursday neck-and-neck in a fierce battle to cross the finish line first in what organisers said was the closest contest in the history of the Sydney to Hobart race.
Just five nautical miles (nine kilometres) were separating the mega-yachts as they raced down Australia's east coast, with defending line honours champion Comanche slightly ahead of Black Jack, Wild Oats XI and Infotrack.
The lead had been switching regularly between 100-footer Comanche and fierce rival Wild Oats XI since a fleet of yachts departed a sunny Sydney Harbour on Boxing Day on Wednesday at the start of the 628-nautical mile (1,163-kilometre) race.
"It is by far the closest race ever," skipper Mark Richards of eight-time line honours Wild Oats XI said from the boat Thursday.
His yacht was first to Hobart in 2017 but was stripped of the win after being handed a one-hour penalty over a near-collision.
"I think it will go all the way to the finish line."
The yachts were off the record pace of one day, nine hours, 15 minutes and 24 seconds set by Comanche last year, amid lighter winds.
The breeze in the notoriously wild Bass Strait between Tasmania and the Australian mainland varied on Thursday, with the vessels supported by 15-25 knot north-easterly winds that weakened at times to six knots.
"It's not usual to have four quite different boats all in the same patch of water," said Black Jack navigator Tom Addis from his yacht.
"These boats are all very different. They all have different strengths and weaknesses. This is the most interesting race in the 100 footers... There's a good chance that we're all going to be together (near the finish)."
TP52 Ichi Ban -- last year's handicap honours winner -- was favourite again to be the vessel that performs best according to size, but dropped off the lead Thursday afternoon.
Smaller boats were in the handicap lead, with Kayimai ahead of Midnight Rambler and Grace O'Malley.
Richards said he expected to cross the finish line in Hobart on Friday morning, but could be slowed if the breeze weakens.
The Commodore of organiser the Cruising Yacht Club of Australia, Paul Billingham, told national broadcaster ABC earlier that the wind was dying amid the "cat and mouse game" between the supermaxis and the close handicap contest.
"The handicap lead is changing every five minutes. There's probably 10 boats that are within an hour of each other on corrected time," he said.
The fleet in the gruelling contest is down to 81 from 85, after Hong Kong supermaxi Scallywag retired early with a broken bowsprit, followed by Zen, Patriot and M3 Team Hungary.
The crews on Thursday afternoon marked the 20th anniversary of the 1998 edition of the race, where a fatal storm saw six sailors lose their lives, with a moment of silence and the reading out of a commemoration message.