"The perk of this job is that I'm always extra hydrated," water sommelier John Zhu tells CNN.
Standing on the 87th floor of the Park Hyatt Shanghai, Zhu swirls the contents of his crystal glass, takes a sniff and goes in for a long sip.
"The taste is so strong," Zhu says. "Do you see how big these bubbles are?"
Zhu's not tasting Champagne -- and it's not Prosecco either.
He's sampling naturally carbonated water imported from Slovenia.
One of just a handful of water sommeliers in China, Zhu has made a profession out of tasting water and offering his expertise to hotels and restaurants across Asia.
A pioneer in this niche industry, Zhu says he's used to being on the receiving end of skepticism.
"People often ask me, doesn't all water taste the same?"
Taste the difference
Although water might seem like a nondescript beverage, Zhu says different minerals give each variation its own unique characteristics.
"Water is just like wine, the sources and minerals determine the taste," he says.
"If the water has a lot of calcium, it tastes sweet and chalky. If it's rich in magnesium, it tastes metallic. If it contains sodium, it tastes salty."
For instance, ROI -- the water Zhu was sampling -- is a Slovenian brand that's said to contain the highest concentration of magnesium of any water in the world, resulting in a strong metallic taste.
To make his case, Zhu brews the same type of tea with five different brands of water from different sources.
As promised, the results vary dramatically.
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Hoping to educate aspiring water sommeliers, Zhu founded Purelogica Academy last year, and now has 70 students training with him.
The majority are hotel frontline staff -- typically in restaurant or bar service -- who were previously unaware of common water blunders.
"It's essential (for staff) to know that the taste of the water can interfere with the taste of the wine," Zhu says.
"If you select a bottle of very elegant and smooth red wine, but pair it with water with high level of carbonation, it could be a disaster."
"The taste of the water is very strong and can easily numb your palate," Zhu adds.
Originally from Malaysia, Ray Sim is one of Zhu's students.
For the past nine months, Sim has been working at The St. Regis Tianjin, China, as the Director of Food and Beverage, overseeing the hotel's dining experiences.
"I met John a few months ago and he shared a lot of knowledge about water with me, which is how I became involved in the course," Sim tells CNN.
"I've been sharing what I've learned with our patrons at the hotel, explaining the difference between soft and hard, sparkling and still water," Sim adds.
"They're very surprised by the concept of water tasting, but are interested to learn more."
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Go with the flow
The price of luxury water might come as a shock to industry newbies.
A bottle of Norway's Lofoten Water, sourced from the Lofoten Islands in the Arctic Circle, can set you back $80.
Zhu explains that just because a water is expensive, doesn't necessarily mean it's better.
The the price of water typically depends on origin -- and whether the extraction point is isolated from any human activity.
"People will say (they are) paying so much for the fancy bottle designs," Zhu says. "But that's not true."
If there's no infrastructure near the source, companies must invest heavily in roads, electricity, piping, waste management and factories.
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Then there's the high cost of transportation and production.
"Because the production volume is so small, (water producers) can't achieve economy of scale," he explains. "Therefore, the price will be more expensive than the water sold to the mass market."
When asked to share his own personal preferences -- if price weren't a factor -- Zhu is noncommittal.
"My favorite water? Changes all the time."