Singer Selena Gomez designed a swimsuit. (Picture: Instagram)

Selena Gomez designed a "high-waisted" bikini to hide her kidney transplant scar for her former assistant-turned-best friend Theresa Mingus' swimwear brand, Krahs Swim.

The 26-year-old singer is helping her former assistant-turned-best friend, Theresa Mingus, launch her new swimwear brand, Krahs Swim, and has designed three limited edition swim styles - which include a plunging red top, a one piece suit and high-waisted bottoms - for the much-anticipated collection, with one bikini created especially to make her feel "comfortable" in her own skin.

In a YouTube video announcing the launch, Gomez said: "The design I did, one of them, it was the high-waisted one with the belt. I've had a kidney transplant and I like bathing suits that kind of cover where that's been and make me feel comfortable.

Selena Gomez's bikini design. (Picture: Instagram)

"I met Theresa 5 years ago. We worked together and became best friends. She has taught me how to see life in a fun, carefree and uplifting way. She has shown me how to be a strong and fearless woman. She is beautiful, kind and smart. I saw how capable she was of achieving her dreams."

And Selena's pal created the collection because she wanted to make every woman feel "confident" and "sexy".

Theresa added: "Every woman wants to feel sexy. Every woman wants to feel confident and beautiful. I definitely want to have a variety of different pieces so everyone can wear them."

And Selena praised Mingus for the business venture, insisting that she is so "proud" of the woman she has become. 

Selena continued: "I'm just excited for people to get to know you, because you've been in my life for so long. You're doing this for other women and you're doing this as a businesswoman so I feel like I'm proud."