The Kookaburras are the number 1 ranked team in the world and go into the tournament as strong favourites, aiming to win their sixth consecutive Commonwealth Games title.
McKeon set a Commonwealth record of 56.78 seconds to beat Groves, whose 57.19 was faster than the time she swam on Thursday.
Gold Coast: Australian boxer Taylah Robertson has become the first medallist of the 21st Commonwealth Games without even stepping into the ring after she got a bye straight into the 51kg category women's semifinals.
"I think change is always going to cause some criticism but I think he's the sort of guy who's happy to take the blame, whether it's his fault or not and that' what a true leader does".
That decision was made by Simon Jones, Cycling Australia's new high-performance chief who made the Gold Coast a priority as a dress-rehearsal for the 2020 Olympics in Tokyo.More news: Trump says he did not know about $130000 payment to Stormy Daniels
Commonwealth Games Federation President Louise Martin said the Duchess was exhausted, rather than bored.
That was 0.374s quicker than a New Zealand foursome had gone before.
The tall, 17-year-old Ruck, however, was arguably the best swimmer on show on Saturday, finishing in a dead heat with Australian Bronte Campbell for silver in the 50m freestyle, then winning bronze in the 100m backstroke some 20 minutes later.
"I told the boys to back off a bit because the shark was right next to us", he added.
Earlier, the Kiwis recorded the second fastest time of 4m 22.331s in qualifying, 0.153s ahead of Canada.