But an innocent dip on a warm and sunny day nearly cost the 57-year-old her life, when a bull shark attacked her on the outskirts of Sydney earlier this year.
"Honestly, I thought I should be dead," Zhang told reporter Dimity Clancey.
She had always considered the secluded and unpatrolled Gunyah Beach in Bundeena as a safe place to cool off.
And on March 7, things seemed no different.
"I had a look at the water. It's actually kind of clear so I said, 'Oh, I might just go for a quick swim'," Zhang recalled.
"I'm not a very good swimmer, so I don't normally go to deep water."
She was innocently doing laps just a few metres off shore when she felt something brush past her under the water.
"I know something stinged me and then there's like a very eerie feeling," she said.
"And then I just saw lots of blood coming out and the water just became too red".
It may have been shock, but incredibly, Zhang said she never felt the shark latch onto her leg and tear it apart.
"I was frozen for a minute," she said.
"From that amount of blood coming out, I didn't actually see the shark."
She didn't need to - she instinctively knew she was in serious trouble and began desperately calling for help.
Luckily, Blake Donaldson and his partner Ellen Melchert had just got out of the water nearby when they heard Zhang's screams.
Heroically, Blake ran straight into the water with his paddleboard to rescue her.
"I wasn't thinking about the shark. I wasn't thinking about my own safety," he said.
"It's either you just watch someone drown or you go out and help them … a couple seconds could mean someone's life."
By the time Blake reached Zhang, she was so weak that she could barely hold onto the board.
"I'm trying to swim and pull as hard as I can, as fast as I can," he said.
Zhang said she felt she didn't "have the strength to do anything anymore".
But they eventually made it to the water's edge, where Melchert used their towels to stem Zhang's bleeding while neighbours called triple zero.
Paramedics rushed to the scene, but Zhang had already lost so much blood that more had to be flown in to save her life.
"I think that I heard people say, 'she doesn't have any pulse'," Zhang said.
"I can't move. I can't even think. I can't breathe."
Shark sightings were already a concern for Bundeena locals before Zhang's attack, with one resident telling 60 Minutes he had a sighting only a couple of days earlier.
But despite those claims, marine ecologist Dr Amy Smoothey is adamant shark numbers are not increasing.
"Everyone's got a smartphone with a video or a camera that allows them to capture and film sharks," she said.
"But it doesn't mean that there are actually more sharks in the area, it's just that we're looking for them more."
Tasked with investigating what happened to Zhang, Smoothey believes she may simply have been in the wrong place at the wrong time.
"The reason why shark bites occur, we don't really know. But what we do know is that humans aren't a food source for sharks," she explained.
"The likely theory associated with why the shark bite happened here is of mistaken identity."
Zhang is just grateful she's alive to tell the tale, even though she still has a long road to recovery ahead.
And when she was reunited with Donaldson and Melchert, the people who helped save her life, she couldn't have been more thankful.
"I don't remember what Blake looked like or Ellen looked like. I just know there's two heroes that [were] there to save me," Zhang said.
"I don't think about it, but then it sort of does hit you and makes you realise that you did save someone," Donaldson said.
A lot went wrong on that fateful day on Gunyah Beach, but thankfully, so much more went right.
"It's unlucky this happened, but it's lucky I have all these people there to support me, to actually send the love," Zhang said.
"Most importantly, I feel lucky I still have my leg."
