America's Cup stars Peter Burling and Blair Tuke bombed in their opening Olympic race, on a bad day for the Kiwi sailing team.
Burling and Tuke, the 2016 Rio Olympics winners and six-time world champions, are the hot favourites in a strong 49ers field but started with a 12th placing.
Only one race was possible on the opening day, when three were scheduled, because of time limits protecting local fishing enterprises.
There was a delay of over an hour because of light winds before the first race attempt, which was abandoned shortly after the start because of unfair conditions.
After a brief delay, Burling and Tuke started badly in the first of the 12 races by losing out in a scuffle with the South Africans, and the legendary Kiwis were second last for a while in the 19-boat fleet.
Robert Dickison and Sean Waddilove from Ireland led for a long periods and pipped Brits Dylan Fletcher and Stuart Bithell in a thrilling finish. Germany's Erik Heil and Thomas Ploessel, the Rio bronze medallists, were third.
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Their struggles continued a day the Kiwi sailors would like to forget.
Alex Maloney and Molly Meech, the Rio silver medallists, had a disastrous start to their Tokyo Olympic 49er FX campaign when they capsized in race one and were disqualified in race two.
The Kiwi sailors were in fifth place when they went into the water during the opening race. While they got the boat back up, they finished a disappointing 16th.
It was a rough start for the leading lights from Rio five years ago, with the 2016 gold medallists Brazil finishing 15th in race one.
A number of leading crews struck trouble as the breeze lifted but the Kiwis fared the worst, with dramatic shots showing both Maloney and Meech plunging into the water as their boat tipped over.
Britain's Charlotte Dobson and Saskia Tidey went on to win the first of the 12 races, ahead of Spain and the USA and followed that up with a win in the second when leaders USA crashed into the water after hitting shifty conditions.
Seeking to pick themselves up after the race one disaster, Maloney and Meech went over the start line early in race two and were disqualified. They continued to sail, heading the field, as they are allowed to do.
In further drama, Spain capsized in the second race and dropped back through the field while there was a crash between Germany and Norway.
Maloney and Meech bounced back in race three to finish fifth, and with the format allowed each crew to drop their worst result from their overall score, the pair sit in 13th after the opening day of racing.
There has been even more bad news for Kiwi sailors, as Sam Meech - brother of Molly - has been left with a mountain to climb to replicate his bronze from Rio.
Meech had yet another tough day at the Enoshima Yacht Harbour and finished 16th in his fourth race - the first of the day - to put him in 19th place overall.
Meech finished one minute and 29 seconds behind race winner Pavlos Kontides of Cyprus, and then finished 14th in race five.
He bounced back with third place in race six to move into 15th overall, but with only four races remaining will need a stellar run of results to make the final.
The same goes for Josh Junior in the Finn class, with results of 12th and 10th on day one placing him 14th overall after two of his 10 races.