PIX: Serena sizzles in single-leg leotard at Aus Open

'If you look up close, it's actually breathable and it's perforated, so it's actually super light and to a point where I need to make sure I'm wearing underwear.'

Serena Williams again wore her distinctive single-legged leotard for her second match at the Australian Open on Wednesday, and said the light material was perfect for the warmer conditions if a little too sheer to wear by itself.

Williams debuted what she has called a homage to Olympic track champion Florence Griffith Joyner, known for her long, colourful fingernails and flamboyant outfits, on Monday to great applause.

"If you look up close, it's actually breathable and it's perforated, so it's actually super light and to a point where I need to make sure I'm wearing underwear," she said, laughing.

"Nude colour, though."

Williams' team at Nike put the design together at short notice including the colour scheme.

"They did everything with this design. I keep texting them after every day, I'm like 'Oh, my God, this is one of my favourites, this is definitely top three, definitely top three for me'."

Melbourne on Wednesday saw the warmest conditions of the two-week event known for its sometimes searing heat as Williams overcame a spirited Nina Stojanovic 6-3, 6-0 on Rod Laver Arena to reach the third round for the 19th time.

"The conditions were fine. I live in Florida," Williams said of the 30 Celsius (86 Fahrenheit) temperature.

Unfortunately for fans, while Nike finished the outfit in time for the tournament, which only got the official go-ahead in December, they did not have time to mass produce the striking design that Williams has worn, she said.

So fans won't find it in the shops.

"The Nike team ... didn't have time to put it in retail," Williams said.