James Guy is under world record pace at 150m. Has he gone too early?

James Guy into an early lead now at the 100m mark...

We are away! James Guy turns the first 50m in third. 

The United States men's basketball team began their charge toward a third straight gold medal with a 119-62 rout of China. 

Kevin Durant scored 25 points and Demarcus Cousins added 17 for the win.

Here are the highlights. 

James Guy looks relaxed, purposeful as he strides out into the pool. It's being tipped to be one of the closest finals in the Olympics...

Next up is the Men's 400m freestyle final. A GB medal?

1 Connor Jaeger United States

2 David McKeon Australia

3 Gabriele Detti Italy

4 Conor Dwyer United States

5 Mack Horton Australia

6 Sun Yang China

7 James Guy Great Britain

8 Jordan Pothain France

Image source, bbc

Golfer Justin Rose has popped in to join the BBC presenters by the pool. He's gearing up for golf's return to the Olympic later this week, and he's loving life in Brazil at the moment.

"This is my first Olympic event experience," he says. "It is amazing. I've been driving past the Olympic village all week and it is great to experience it.

"I believe in it [golf at the Olympics]. It can help grow our game and it is the pinnacle for most sports, so why not for us too?"

That's how to make a final! Sweden's Sarah Sjostrom clocks 55.84 secs, just outside of her own world record!

Emma McKeown of Australia was second. 

Smiles all around after GB beat Australia 2-1 in the group stages.

That first semi final was won in a not particularly fast time. So there could be more qualifiers from number two. Away!

There is British interest again the men's 400m free final (02:30 BST) as James Guy looks for a medal. He won silver in last year's worlds.

American Conor Dwyer was the fastest qualifier - he clocked three minutes 43.42 secs.

Image source, AP

Here's the line up for the second semi:

1 Kimberly Buys Belgium

2 Emma McKeon Australia

3 Lu Ying China

4 Sarah Sjöström Sweden

5 Penny Oleksiak Canada

6 Chen Xinyi China

7 An Se-hyeon South Korea

8 Natsumi Hoshi Japan

And it is 16-year-old Rikako Ikee who takes it from Dana Vollmer. Jeanette Ottesen is third. All into the final. 

A 16-year-old and a 28-year-old in this first semi-final. Spanning the ages...

Rebecca Adlington
Double Olympic gold-medal winning swimmer on BBC One

I am so, so pleased for Max. Getting fourth in your first global final and coming here and doing two personal bests. He is only 21 and has such a bright future.

Max Litchfield, speaking to BBC One: "Shame to just miss out on a medal but two PBs in one day, I can't complain at that.

"There are places to improve, I'll come back next year and come back better."