The swimmers are just bobbing around in the water waiting to go. The hooter goes and we're off.

They have to go 350m slightly to their right from the starting line and then head into the direction of Sugarloaf Mountain.

Two minutes down now, about two hours to go...

You can watch the start of the race at the top of this page on BBC Two (if you're in the UK). If you want to watch the whole gruelling two-hour race, then click on this page, or else watch on the Red Button on your TV.

We are almost ready to go now in Rio.

Keri-anne Payne and her 25 competitors begin the 10km swim from Fort Copacabana by walking into the water from the beach and then starting in a line. 

The original starting pontoon was swept away in the waves and ended up on the beach on Friday night, and organisers have been unable to secure their replacement pontoon over the weekend. 

Windsurfer Nick Dempsey won a third Olympic medal after claiming silver in Rio on Sunday. He's now set to retire but can he be persuaded to carry on until Tokyo in 2020? He's answering your questions now via our Facebook page, external.

Image source, BBC Sport

Keri-Anne Payne takes on the 10km swim and she gave Get Inspired a few of her best swimming tips. You can watch them by clicking here.

But Keri-anne Payne, who won silver at the 2008 Games, has learned from London 2012 and her tactics have changed.

"After Beijing and in the lead-up to London, I had a very specific race plan and it was to go out in front. When things go wrong, it's not necessarily the best option, so that's why I've been working on all my options. Every eventuality I've tried and tested.

"Everything has been about me doing as well as I possibly can to stand on that podium. I've taken myself out of my comfort zone, done some really crazy, silly things, races I never thought I'd do."

Things have changed for Keri-anne Payne in the past four years. She was the first British athlete to qualify for London 2012, all the way back in July 2011. 

But this time she only got through by finishing second in the very final Olympic qualification event in June.

After that, she told BBC Sport: "It totally was emotional and hasn't really sunk in, but I'm definitely going to cry later - tears of happiness.

"I have put so much into this last four years and I'm so happy that it's all paid off in the end.

"Coming fourth at a home Olympics was the worst place to come and I took a year out after that, but I just decided at one point I needed to fully commit to it. Getting back into training was hard, but I have loved the journey - even today when I was elbowed in the face!

"Everything I've done is to get prepared to stand on the podium in Rio. I'll be doing everything that I can to make that happen."

Image source, Getty Images

Here's a rundown (pardon the pun) of Team GB athletes competing in the morning session in Rio: 

Women's 200m heats

13:54 (BST) Dina Asher-Smith goes in heat five 

14:06 Jodie Williams in heat seven

Men's steeplechase heats

14:25 Rob Mullett goes in heat one

Women's hammer final

14:40 Sophie Hitchon

Men's 400m hurdles heats

15:56 Sebastian Rodger in heat four 

16:03 Jack Green in heat five

In the evening session we'll have:

Men's 110m hurdles heats

00:56 Andy Pozzi is in heat three

01:12 Lawrence Clarke in heat five

Women’s Discus Qualification 

01:50 Jade Lally

Women’s 400m Hurdles Heats

02:10 Eilidh Doyle in heat six

Image source, Getty Images

Britain's Keri-anne Payne, who is the joint fourth favourite today with the bookmakers, will be hoping to make up for her London 2012 heartbreak.

She finished an agonising 0.4 seconds outside the medals - in a race which takes almost two hours - as Hungary's Eva Risztov won gold.

The 24-year-old, as she was then, had been in the leading pack throughout but despite a late surge, could not overhaul Italy's Martina Grimaldi for bronze.

 "I just made a bad decision on the third lap," she said after the race. "I knew we had to feed, but it was a bad decision [to do it then] unfortunately."

Britain's Charlotte Dujardin is bidding to become the second British woman in the space of three days - following cyclist Laura Trott - to claim a third Olympic gold as she looks to retain her individual dressage title with horse Valegro.

Dujardin has already won silver in the team event and is also the reigning world, European and Commonwealth champion. We're sure she's got room for a few more trophies, though. 

Dujardin gets underway at 16:40 BST, after compatriots Fiona Bigwood (14:30) and Carl Hester (15:35). 

Image source, Getty Images

Keri-anne Payne tweeted this last night. I hope her nail polish is waterproof. Wait, is all nail polish waterproof? I've been brushing up on my 10km swimming, but didn't think of doing make-up research too.

The first gold medal on offer on Monday comes in the women's open water swimming event, which starts at 13:00 BST.

British two-time world champion Keri-anne Payne is involved and looking to make up for the frustration of finishing fourth in the event at London 2012.

Payne and her 25 competitors will begin the 10km swim from Fort Copacabana by walking into the water from the beach and then starting in a line. 

The original starting pontoon was swept away in the waves and ended up on the beach on Friday night, and organisers have been unable to secure their replacement pontoon over the weekend. 

Image source, Getty Images

Liverpool captain Jordan Henderson congratulates world record breaker and Reds fan Wayde van Niekerk after he won gold in the 400m on Sunday night.

"Congratulations to @waydedreamer, external on becoming Olympic champion and setting new world record. Amazing performance from a big LFC fan"

Wayde van Niekerk's sensational record-breaking run in the 400m won South Africa their first gold medal of Rio 2016 and, even though he stunned most people watching, Usain Bolt knew the 24-year-old was capable of.

"Usain has been such a huge rock, inspiring me as an athlete," said Van Niekerk.

"He told me back in Jamaica that 'you will break the world record'. And he came to me after and said 'I told you you could do it'."

Image source, AP

Jessica Ennis-Hill had a front row seat for Usain Bolt's win in the 100m as she and the other heptathlon medallists had just received their medals. They certainly made the most of it as they got one of the best selfies ever...

Steve Cram
BBC athletics commentator on BBC TV

Justin Gatlin got out, but then, as ever, Usain Bolt got those legs moving and you can't stop him. He delivers once more.

We have had a fantastic night in the stadium and Bolt has added to it in his own style. He has two more gold medals to win for sure.

If it was in old Greek times they would put him on Mount Olympus and they would call him the God of Speed.

After his 100m win last night, Usain Bolt told BBC Radio 5 live: "It's brilliant. It's relief. It's been such a build-up, I didn't notice how nervous I was until I started competing. It wasn't until I started competing I thought 'this is big'. 

"I've come here to prove to the world again and again that I'm the greatest. This Olympics will put me amongst the greats and that's why I'm here.

"I'm definitely coming to London for the World Championships. We haven't made the decision whether I'll run one or two events, but I'll be in the 100m - no problem. 

"My coach tells me to take it a year at a time and don't talk about retirement. I'm feeling good so we'll see what happens."

There's something quite special about taking in the big sporting moments on the radio.

Have a listen to how Mike Costello described Usain Bolt's 100m gold on BBC Radio 5 live.

Spinetingling.