Farmers are flooding social media with images of their farm stream water as anger grows over a display at Te Papa.
National MP and agriculture spokesperson Todd Muller earlier tweeted a picture of the bottle of dyed brown water which is part of a display in the museum's Te Taiao Nature exhibition.
It is labelled as "water from a typical farm stream" with the image of a cow defecating in a waterway, and was classed as undrinkable.
Muller said the fact the water was not from a real dairy farm was outrageous.
"It's so disappointing as we've been working really hard to protect water," he said.
He said the displayed water wasn't reflective of the water on an average New Zealand farm.
"The image of a cow standing in water defecating is also not reflective of the reality that dairy farmers have fenced over 98 percent of waterways."
In response to Muller's concerns, Te Papa said the display showed that water quality can't be judged on its appearance.
"The dairy stream example is one of nine, and sits right next to a city stormwater bottle and below a forestry stream water bottle"
Te Papa spokeswoman Kate Camp also told Stuff that the bottles had been created for display purposes only and were not samples.
"The water in each bottle is dyed to symbolise different kinds of water," she said.
"This display is about telling the story of New Zealand waterways. It's based on robust research that shows that many waterways in New Zealand - in urban and rural areas - aren't fit to drink or to swim in."
Meanwhile, Muller encouraged farmers to post a bottle of water from their farm streams to compare it with the one displayed by Te Papa.
Northland farmer, Andrew Booth was among them, posting a video from his farm which showed him drinking clear water from the Mangakahia River.
"Since finding out what Te Papa has on display, and labelling it farm water, I thought I'd show you what some of the rural waterways around New Zealand actually look like," he said
"It runs through my dairy farm and plenty of other dairy farms further up the catchment and beef farms as well."
The video shows Booth drinking the water from a jar.
"This is the water, look at that beautiful water."