The sun was shining like it was a Californian summer's day, and although the stadium is a long way from the beach, 40,000 fans rode the wave of the smooth harmonies and almost achingly beautiful lyrics of the Beach Boys.
They couldn't be seen in the front of the North Stand but they could certainly be heard as they kicked off with Surfin USA, with a smooth segue to Barbara Ann.
Band member Bruce Johnston called it the "Super Bowl of rugby" as fans in the South Stand rocked out almost as much as they did for the Harlem Shake.
Lauren Jones, a South African who flew in from Singapore, said: "It was amazing, my uncle used to play these songs as a child. I know all the words, everyone does, it takes me back."
She was resplendent in green, dressed as a bottle of champagne, and all over the stadium fans were popping their cork for the natural synergy of rock 'n' roll and rugby.
Riddling it over in the west side in a box, Nic Oven said: "At first I'd wished they'd brought Neil Diamond. I have to say I was sceptical, but I didn't think it would be this good. I'm sold. I just wish they hadn't lost the big screen on the North Stand, it was a better resolution, perfect for watching replays and would have been excellent for the Beach Boys."
"I saw them 33 years ago in Auckland and their harmonies are better now," said Australian Marie Sigg, who was in the crowd with husband Rob and son Morgan, a former professional rugby player.
As the Beach Boys performed, the Kukri girls flashed their abs and silver pom poms, and Cathay Pacific girls in red suits looked like sartorially elegant back-up singers.
The Beach Boys were delighted with the performance as they mingled in the HKRFU box with players and officials from Kenya to Mumbai.
"We are always all about sport and, although we have a heritage in watersports, these days we perform at many sporting events," said Johnston, who joined the band in 1965.
The Beach Boys, on their 50th anniversary tour, looked fresh despite playing at the Venetian in Macau the night before. This may have been one time their loud shirts blended in with the crowd as many looked like they needed a volume control. Many fans were disappointed the stage was not in the centre of the pitch, but HKRFU chairman Trevor Gregory said this was "logistically impossible".
"I never expected it would be this good," Gregory said of the 36-minute set. "It's far exceeded our expectations and the Beach Boys rocked the Sevens.
"Sure, some people have said they'd have liked to see the stage on the centre of the pitch, but that just wasn't logistically possible. This has added a whole new dimension to the Sevens party."
When asked what Beach Boys' song the Sevens reminded them of, founding member Mike Love, who wrote most of the lyrics for the songs, agreed it was "Fun Fun Fun."
"We play that at every concert we perform," Love, 72, said.
"It's what we represent and it's what the Hong Kong Sevens is all about. The audience was good, the sound was good, we were honoured to be invited here. It was the first time they've had a band perform live at the Sevens, and we'd come back and do it, again."
Many of the younger generations didn't know the Beach Boys from the Pet Shop Boys, or even that the mini concert would be held in the afternoon and complained about the stage positioning.
Justin Xiang and Mark Chearavanont, both 15 and taking their spring break from schools in US, were sitting at Block 314, the far end of the East Stand next to the South Stand.
It was hard for them to realise where actually the performers were.
"I hadn't heard of any Beach Boys' songs before but I think they are good. It took me almost 10 minutes to find the performers.
"They were too small to be seen from my stand," said Xiang.
Chearavanont knew about the band and said his stand's reaction was quieter than others.
"It's perhaps because of the distance.
"The music was good but that was simply too far away. They should have put the stage at the centre of the pitch," said Chearavanont.
Claire Marshall, 18, a first year economics student at HKU was with her boyfriend, actor Georgie Tedest, 19.
"At first I thought I was just listening to music played from a CD when the show kicked off. I only realised where the singers were when my friends pointed them out," said Marshall.
"The stage should be in the middle of the stadium."
The pair said the top of their wish list for next year's performance was Cold Play or Red Hot Chili Peppers.
Scott McLean, managing director of International Light & Sound, the Hong Kong-based event and entertainment company that produced the show, said it all went off as planned.
"It was fantastic, for the first time at the Sevens to do a band like that. It went well and I think everybody loved it.
"There is a lot of co-ordination and communication necessary between everybody from the rugby union, the stadium and the production team.
"We started on Monday setting up and the rain set us back on Wednesday and also on Thursday [sound-check day].
"But by Thursday night we had it all together. There are always going to be issues to deal with it, particularly when you try something for the first time. In the end it went off as planned. The Beach Boys loved it, they thought the whole experience was great."