It's been a day of frustration for New Zealand athletes at the Olympics overnight.

Jo Aleh and Polly Powrie suffered a major setback in their Olympic women's 470 title defence when they were disqualified for a start line infringement early in the first race, their sixth of the regatta at Guanabara Bay.

They stayed in the race and went on to cross finish line first but, unless they can overturn the ruling, they pick up the maximum 21 points.

Ryan Fox and Danny Lee, after struggling and falling out of medal contention yesterday, finished the event with rounds of 68 and 69 to be currently placed in the bottom half of the field.

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However, it's shaping up to be a thrilling finish in the fight for the gold medal with Britain's Justin Rose and Sweden's Henrick Stenson going blow for blow in the early stages of their final rounds.

Elsewhere, synchronised swimmers were greeted by clear blue water in the competition pool today after officials worked through the night to replace murky green water that's become a big embarrassment for Rio Games organisers.

IOC spokesman Mark Adams says reports of American swimmer Ryan Lochte being robbed at gunpoint are "absolutely not true," despite reports of his mother telling media otherwise.

Russian swimmer Yulia Efimova has described her Rio Olympics experience as a nightmare after coming under fire from US rival Lilly King

While US decathlete Ashton Eaton has had to defend himself after being labelled a traitor on soial media for wearing a "Canada" hat while supporting his Canadian heptathlete wife.

However, most eyes weren't focussed on what has already happened in the Games and instead were looking forward to what promisses to be a huge day of action ahead.

Our track cyclists are back in action with the start of the women's sprint and men's omnium events while the men's Black Sticks take on Germany in their quarter-final fixture.

The rest of the world will be watching Usain Bolt race for an historic third Olympic gold medal in the men's 100m sprint while US gymnast Simone Biles will be looking to add to her golden medal haul in the individual events today.

Also of interest is Andy Murray in the men's tennis as he attempts to become the first man to win two Olympic gold medals in the singles event.

In progress/still to come:

Monday August 15

Sailing:

Finn class - Josh Junior, Race 9 4.05am, Race 10 5.30am

Sailing:

Women's 470 - Jo Aleh and Polly Powrie, Race 7 4.05am, Race 8, 5.30am

Sailing:

Nacra - Gemma Jones and Jason Saunders, Race 10 4.05am, Race 11 5.05am, Race 12 6.05am

Sailing:

Men's 49er - Peter Burling and Blair Tuke, Race 7 4.15am, Race 8 5.40am

Cycling:

Track - Women's sprint qualifying, 1/16 finals (if qualified) - Olivia Podmore, Natasha Hansen, 7am

Cycling:

Track - Men's Omnium - 15km scratch race 7.40am, 4km pursuit 8.50am, elimination race 10.42am - Aaron Gate, Pieter Bulling, Dylan Kennett

Weightlifting:

Women's +75kg group A - Tracey Lambrechs - 10am

Hockey:

Men's quarter-final, 11:30am

- with AP