While they both won, things were a little tougher for double sculls combinations Eve Macfarlane and Zoe Stevenson and Chris Harris and Robbie Manson, with the men just edging out Azerbaijan on the line.
The men's lightweight four of James Lassche, Peter Taylor, Alistair Bond and James Hunter underlined their medal credentials with a sound win, in the fourth-fastest time.
The quad's struggles came as no surprise, having qualified belatedly after a Russian crew were ruled out five weeks ago following a doping violation.
Jade Uru, Nathan Flannery, George Bridgewater and John Storey were 7sec behind heat winners Estonia and ninth-quickest out of 10 crews.
The New Zealand women's sevens team meanwhile showed off their class by recording two convincing victories in their opening pool matches at the Deodoro Stadium as the Olympics welcomed rugby sevens into the fold.
The Kiwi team smashed Kenya 52-0 in their opening pool match, before following it up with a 31-5 win over Spain.
It took only 13 seconds for star flyer Portia Woodman to cross for the first try of the tournament and it was all one-way traffic from there as the gold medal challengers overpowered and overwhelmed the Kenyans.
Portia Woodman and Kayla McAlister each scored a double in the eight-try rout.
McAlister was again the stand-out in the second pool match, troubling the Spanish defence all game.
The Kiwi side will meet France in their third pool match tomorrow, before the quarterfinals.
On the hockey turf, a second-half fightback gave the Black Sticks a glimmer of hope, but gritty defence laid the base for Australia's 2-1 win in their opening men's hockey match at the Rio Olympics.
The world No.1 Australians went into the break with a two-goal lead through Chris Ciriello and Matt Gohdes, but the Kiwis hit back barely 60 seconds after the restart when James Coughlan found the net.
New Zealand thought they'd found an equaliser when Hugo Inglis deflected in a vicious cross from Hayden Phillips only for the video referee to rule it out.
It was a largely forgettable opening day for New Zealand's swimmers, with only breaststroke specialist Glenn Snyders advancing out of his heat.
It initially looked as if Snyders would have to swim-off for a place in the semifinals after recording the 16th equal fastest time with Hungary's Daniel Gyurta. But the Hungarian opted not to take part in the swim-off, allowing Snyders to take the last remaining spot in the semis.
Britain's Adam Peaty was fastest qualifier, posting a sizzling world record time of 57.55 in the heats.
Helena Gasson finished last in her heat of the 100m butterfly, with her time of 59.82 about 0.3 of a second off her personal best.
Matt Hutchins was more competitive in the 400m freestyle, finishing second in his heat. But his time of 3:48.25 - a PB - placed him 19th overall, just off the semifinal pace.
A shattered-looking George Bennett has finished well down the field in the arduous men's road race at the Rio Olympics.
Bennett, who lost teammate Zac Williams after 40km, finish almost 12 minutes behind the winner, Belgium's Greg van Avermaet who outsprinted Dane Jakob Fuglsang at Fort Copacabana with Pole Rafal Manejka taking the bronze.
Bennett, who featured in a group of chasers that tried to reel in a breakaway about 40km from the finish, coasted across the line in 33rd place after a drama-packed 237.5km littered with crashes and numerous withdrawals.
Sunday August 7
Rowing: Women's single scull heats (Emma Twigg) - first place (qualified for quarter-final)
Cycling: Men's road race - George Bennett - 33rd, Zachary Williams - DNF
Equestrian: Eventing Team Dressage Day 1 - Mark Todd - seventh (44.00 points), Tim Price - 13th (47.00 points) Jonathan Page and Jonelle Price to compete tomorrow
Gymnastics: Men's artistic individual qualification - Mikhail Koudinov - all round performance 80.899
Rowing: Men's pair heats (Hamish Bond and Eric Murray) - first place (qualified for quarter-final)
Tennis: Men's doubles first round, from 1.45am
Rowing: Women's double scull heats (Eve Macfarlane and Zoe Stevenson) - first place (qualified for semi final)
Rugby sevens (women): Pool game - New Zealand 52 Kenya 0
Rowing: Men's double scull heats (Robbie Manson and Chris Harris) - first place (qualified for semi final)
Rowing: Men's lightweight four heats (Alistair Bond, James Hunter, James Lassche, Peter Taylor) - first place (qualified for semi final)
Rowing: Men's quadruple scull heats (Jade Uru, George Bridgewater, Nathan Flannery, John Storey) - fourth place (through to repechage)
Swimming: Women's 100 butterfly heats , Helena Gasson - eighth in heat, 33rd overall
Hockey: Pool match - Men's Black Sticks 1 Australia 2
Swimming: Men's 400m freestyle heats - Matthew Stanley (withdrew), Matt Hutchins - second in heat, 19th overall
Men's 100m breaststroke heats - Glenn Snyders - sixth in heat, 16th overall (qualified for semifinals)
Rugby sevens (women): Pool game - New Zealand 31 Spain 5
Football: Group G - Football Ferns v Colombia, 11am.
