Copa beach volleyball on, shirts off

Copacabana is usually packed with people in skimpy clothes playing beach sports, but now it's happening for a gold medal.

Thousands of rowdy Brazilians lined up for hours to get into the stadium built on Rio's most famous beach to watch the gold medal favourite home team start their Games on Saturday.

They booed the Canadian players as they lined up to serve against Brazilians Alison Cerutti and Bruno Schmidt and fired up as Cerutti urged them on to make more noise.

There seemed to be only three options for the Brazilian fan uniform - yellow shirt, bikini, or no shirt.

Unfortunately the stadium was only about 40 per cent full when the Brazil-Canada game started, thanks to long lines at security keeping fans out.

Former Australian Olympian Natalie Cook said the stadium was the best she had seen, as it was designed to give fans a view of the waves as well as the action.

"It's spectacular," she said.

"I've been here 25 times, I love these people.

"They walk around with no clothes on ... no shirts, all in bikinis... it's amazing."

Outside the venue, no-shirted locals asked Australian players Louise Bawden and Taliqua Clancy for selfies and high fives once they recognised the Olympic uniforms.

"The atmosphere is fantastic and everybody gets into it," Clancy's grandmother Jocelyn Clancy said.