"I was lucky enough to be onboard when we cruised through Europe for six months,' she says.
"We went to France, The Netherlands, England, Italy and Spain.
"I crossed the Atlantic Ocean with the ship, and now we alternate between the Eastern and Western Caribbean."
The ship itself - the largest passenger liner in the world with a capacity for 5479 guests - boasts a 2100-strong crew, of which 20 are performers at the AquaTheater.
It also has 23 swimming pools, two surf simulators, an enormous water slide and a staggering 20 restaurants - so it took a while for her to find her way around.
Performers typically stay on the ship for six to nine months at a time, Sydney says - although she's just completed 11, putting on regular shows for their spectators.
"We always begin with rehearsals at our entertainment facility in South Florida and then have about two weeks to bring the show to life onboard," Sydney explains.
Two weeks doesn't seem long when you see the elaborate performances - one dubbed The Fine Line, an acrobatic aqua show and the other called Big Daddy's Hideaway Heist, a display that combines comedy and diving.
So does she ever lose her nerve?
"Not anymore,' she says. 'When we opened the show, I was definitely nervous for the first couple of weeks. And there are still times when the ocean is not as smooth, which can make things interesting."
She adds: "The AquaTheater has the deepest pool ever built on a ship, and when we're moving from side to side, the water in the pool can spill out.
"If it's unusually rough weather and we lose too much water, we postpone shows - a safety precaution for our divers who are jumping from as high as 17m (55ft). This is uncommon though."
Sydney started gymnastics at the age of only one and a half and enjoyed a brief stint some years ago with the Cirque du Soleil, and insists there are very few downsides to her globe-trotting life.
"The hardest thing about living at sea is being away from family and friends during the holidays," she admits.
"But other than that, I never get seasick, my expenses are next to nothing, and I have made friends for life onboard."
And as for the next decade of her life?
"That's the million dollar question,' she responds. 'I have no idea. Right now, I'm happy making the most of each day."
