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The ad features a happy-looking young man dipping into a stream and looking refreshed after a sip of the clear, cool-looking water.

“The earth constantly offers the purest substance on the planet as spring water,” the site explains.

“This water is magical.”

Unfiltered, untreated, unsterilized spring water flows into a bottle at Opal Springs Water Company in Culver, Oregon. Leah Nash / The New York Times/Redux Pictures

And for just $16 a jug, plus a $22 deposit, customers can have some of this “live” water, also.

The company selling this “live” water says it’s providing toxin-free water, but anyone drinking from a stream or even a spring is getting a stomach full of bacteria, parasites and viruses that may or may not be harmful, say food safety experts.

They could also be getting a mouthful of farm waste runoff, septic tank spillover, chemicals and pesticides, the Centers for Disease Control and Prevention, Environmental Protection Agency and various health departments caution.

“By the time the spring reaches a collection point, it could have chemicals, bacteria, parasites and viruses in it that might make people sick. Waterborne organisms (Cryptosporidium, Giardia and E. coli) can cause symptoms such as nausea, vomiting and diarrhea,” according to the New York state department of health.

Related: NC water park linked to brain-eating amoeba

“Spring water could also contain chemicals that can cause long-term health effects, such as kidney and liver damage, nervous system disorders and birth defects. The health effects of drinking contaminated water can be more severe, even life threatening, for babies, children, the elderly and immune-compromised individuals.”

“Consenting adults are allowed to be stupid."

There’s nothing new about people advocating for purer water, or about people claiming spring water is somehow better than tap water.

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But a New York Times article highlighting the “raw water” movement in California has upset health professionals like Dr. Mary Margaret Fill, medical epidemiologist who specializes in water-borne diseases at the Tennessee Department of Health.

“I was surprised and then a little disappointed,” Fill said. “We know that the United States has some of the safest drinking water in the world. Drinking untreated environmental water carries risks. We know that it can be contaminated with a whole host of things.”

Anyone who has suffered through the weeks of misery brought by Giardia — a microscopic parasite that causes cramps and diarrhea — would advise others to steer clear of untreated spring or stream water, said Fill.

Tap water is tested for bacteria, viruses, chemicals and other contaminants. While the system occasionally fails — the lead contamination in Flint, Michigan being a notable and frightening example — it’s still a step up from drinking water that can carry cholera, typhoid and other killers.

Every year there are cases of disease where the only identifiable exposure is either untreated environmental water or undertreated water, Fill said.

“Consenting adults are allowed to be stupid,” said Bill Marler, a food safety attorney in Seattle. “But we have to make sure we warn people who are vulnerable, like kids and the elderly, or cancer patients.”

The natural water advocates selling their products online or to grocers in trend-friendly neighborhoods say their product is not only clean and pure, but carries beneficial bacteria.

“Shocking but true — All other filtered and even bottled spring waters are sterilized with UV light, ozone gas, and a sub micron filter,” the Live Water website claims.

“This is similar to how most juice and dairy products are pasteurized for shelf stability. Unfortunately this sterilization destroys beneficial sources of minerals and probiotics.”

Related: Two dead from raw milk cheese contaminated with listeria

Yes, it's true, the EPA and CDC say. These treatments kill off potentially deadly germs and filter out poisonous minerals such as arsenic.

“The micro biome (sic) of our gut produces about 95 percent of the serotonin and 50 percent of the dopamine in our brains,” the site goes on, without attributing this. NBC News was unable to find any legitimate source to support such a claim, which is biologically dubious.

“There could be countless other benificial (sic) microbes present, scientists just haven't discovered yet. They are imperative for optimal physical and mental health. Without these probiotics we're not able to fully assimilate all the nutrients in our food,” it adds.

"That's just ridiculous," Marler said. “People have been digesting food for a long time without the aid of special water."

While it’s true the microbiome is important, science hasn’t yet figured out which bacteria in and on our bodies are helpful, Fill noted, or whether people need to get them from outside sources.

"Public health and medical experts consider water treatment to be one of the most significant public health achievements of the 20th century."

“We all have bacteria that live all over our skin and in our intestine and in our bodies that help keep us healthy,” Fill said. “I don’t know how you acknowledge that there are potentially good bacteria in water without acknowledging that there are bad bacteria, too."

Plus, Marler points out, anyone selling water that sickens people is open to being sued.

Wells fed by aquifers routinely sicken people. Top causes, according to the CDC, include hepatitis A, Giardia, Campylobacter bacteria, Shigella bacteria, E. coli bacteria, Cryptosporidium, Salmonella, and chemicals such as arsenic gasoline and nitrates.

“It is important to take a step back and realize that public health and medical experts consider water treatment to be one of the most significant public health achievements of the 20th century,” Fill said.