Serena Williams posted photos and a video to her Instagram in which she was seen having some fun basking in the sun with her daughter, Olympia Ohanian, three.

The tennis star, 39, was twinning with her daughter as both wore hot pink Nike swimsuits on Tuesday.

Even Olympia's favorite doll Qai Qai was included in the fun, sporting a matching swimsuit of her own.

Serena seemed impressed that Nike had thought to create a suit for Qai Qai as well.

'When @nike makes a swimsuit for not just @olympiaohanian but @realqaiqai too. How amazing is this @ehrmannspartners view?' she captioned the shot, also tagging French architectural design firm Erhmann's Partners.

The bright pink one-pieces were embossed with Nike's logo across the front in white lettering, with the 'i' replaced by the athletic brand's signature swoosh.

The Wimbledon champion's swimsuit showed off her toned legs and sculpted arms as the trio relaxed in a blue lounge chair by the pool.

She went makeup-free for the posts with her long sun-streaked waves tumbling around her shoulders.

Olympia's hair was pulled back and she smiled broadly as the three posed on front of a lake.

In the video, Serena leaned back on the lounge chair as Olympia tried make Qai Qai sit up only to have the doll fall over.

The 23-time Grand Slam winner smiled as she reached forward to help her daughter.

In a cute touch, she added P!nk's new song with her own nine-year-old daughter, Willow Sage Hart, Cover Me In Sunshine, as background music for the video.

She captioned the video, 'Covered in sunshine just like the resort.'

Serena shares Olympia with her husband, Reddit founder Alexis Ohanian, 38. The sports icon and the tech entrepreneur married in 2017, five weeks after Serena gave birth to Olympia.

The couple gave Qai Qai to Olympia and the doll became an instant sensation on social media, with almost 300,000 followers on her own Instagram page.

Alexis and Serena have joked that they consider themselves to be Qai Qai's grandparents and they staged many fun photo ops with the doll after she made her first appearance at the 2018 Australian Open.

During a press conference at the competition, Serena explained why she gave Qai Qai to Olympia.

'I wanted her to have a black doll,' Williams said. 'Growing up, I didn't have that many opportunities to have black dolls and I was just thinking, you know, I want her first doll to be black.'