Indeed, National had decided to set maximum pollution levels such that rivers would be safe enough for wading and boating - but there was no requirement for them to be swimmable.
"New Zealanders want to be able to swim in their local river, but National's plans offer nothing better than the ability to wade in them," Green Party water spokesperson Eugenie Sage said.
"If the Government wants to turn our rivers into drainage ditches, then it should come clean about that."
Last year, government monitoring found that 61% of recreational sites on rivers were unsafe for swimming. National then admitted last month in Parliament that it was planning to drop its annual reporting on whether rivers are swimmable - as though the problem with river health might disappear if we just stopped looking at it.
While National's policy floundered in the shallows, the opposition wasted no time.
Two weeks after the government's policy announcement, the Greens jumped in to announce their own river policy, declaring it one of their top election priorities.
They vowed to establish a protected rivers network (akin to giving some rivers National Park status); to take a strong stance on water quality, making all rivers safe for swimming again; and to prohibit new dams on any still-wild rivers.
In early August, Labour joined the fray as well, announcing a water policy in partial agreement with the Greens. Their top priorities: making all rivers and lakes "swimmable, fishable and suitable for food gathering"; getting farmers to pay for using big irrigation schemes; and opposing privatisation of water resources.
The Government, on the back foot, turned to the age-old combat tactic - that of playground name-calling. The Greens' proposal was "the latest step in their anti-jobs, anti-growth, stop-everything manifesto," declared a Beehive press release.
Surely making rivers swimmable should not be "dictated... by politicians in Wellington", Amy Adams said. As for Labour, she called their water proposal an "anti-jobs attack on rural New Zealand".
Meanwhile, Gareth Morgan commissioned a report critiquing the new government policy, drawing on the advice of 16 leading freshwater scientists. The report pointed out that the government's standards for nitrate toxicity were totally inadequate, set at a level where nitrates would be toxic to 20% of aquatic species - a significant level of ecosystemic failure.
The Morgan Foundation's report put the scientists' alarm in plain words: "The analogy used is that an alcoholic is sick long before their liver fails."
Morgan has started a "MyRiver" website - garethsworld.com/myriver - to encourage average New Zealanders to become activists, protecting their rivers and influencing policy.
It wasn't always this bad, of course. The sudden growth of New Zealand's dairy industry has caused freshwater quality to decline rapidly in recent decades.
The countryside has gained 125% more cows in the past 30 years. The soaring number of bovine bladders has meant a whole lot more urine going onto the ground - and from there reaching groundwater and rivers.
Dairy farming contributes 38% of the nitrogen runoff that ends up in New Zealand waterways. It's not just humans that are losing their swimming holes; 74% of New Zealand freshwater fish species are now listed as threatened.
Jan Wright, the Parliamentary Commissioner for the Environment, issued a dire warning in a November 2013 report: "If we continue to see large-scale conversion of land to more intensive uses, it is difficult to see how water quality will not continue to decline."
Still, many of those champions of water quality are pointing fingers not at individual farmers, but at government policy.
Massey University scientist Dr Mike Joy, an outspoken rivers advocate, spelled it out in a recent lecture to the Royal Society: "Decades of minimal regulation of impacts from government has been the major factor contributing to the crisis we now have," he said.
"Poor practices have been incentivised; with no penalty for pollution, farmers have been pushed by the industry to maximise profit at the expense of our waters."
Labour and the Greens have not specified exactly how they would get New Zealand's rivers back into healthy swimmable condition.
Nonetheless, as the political parties stake out opposite positions, the September 20 election appears set to influence how clearly our rivers flow into the future.
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