The world number one, who is looking to add a first Melbourne Park crown to the French and U.S. Open titles she won last year, was all business as she whipped through the first set in 23 minutes.
World number 100 Bucsa had simply no answer to Swiatek's all-court game and the Spaniard only managed to avoid the dreaded 'double bagel' 6-0 6-0 scoreline by holding her last service game.
"My main goal was to keep my focus till the end because sometimes it's hard when you feel like you control everything, your mind can wander off," Swiatek said.
"I'm pretty happy that I was solid till the end. I didn't really let Cristina play her game. I know she can be solid, so I'm pretty happy that I was just disciplined.
"A couple of years ago when I was in the fourth round I was really exhausted, and right now I feel this is the right place to be.
"Hopefully I'm going to continue to play solid and hopefully I'm going to play more matches here."
Swiatek has made at least the fourth round at Melbourne Park for the last four years and said she felt she was right where she should be heading into the second week of the year's first Grand Slam.
"I feel I'm more and more confident since day one here. I'm not even talking about matches, but also practices," she added.
"I feel like I've done so much work to feel more confident, more relaxed on court. I'm pretty happy that I did it because it's just a little bit easier. When you actually played those matches, you can feel the rhythm a little bit more."
Swiatek should face a tougher test in Wimbledon champion Elena Rybakina in the last 16 after the big-serving Kazakh earlier upset last year's losing finalist Danielle Collins.
"We played recently in Dubai," said Swiatek of Rybakina, the 22nd seed. "It wasn't a tournament, it was an exhibition. So we know each other pretty well.
"We also played in juniors, but you know, we both made such a progress that it doesn't really matter what happened a couple of years ago."
"For sure she's very strong physically and mentally," Moscow-born Kazakh Rybakina said, eyeing up the challenge. "I will have to take all my chances. I think Iga is a great player."
