He believed current freshwater policy wasn't serving the best science - or making a difference where it needed to.
"There are so many examples from around New Zealand where policy says one thing, but we see another thing happening in reality."
Joy was also concerned about the self-reporting nature of councils and government around freshwater - and the potential for spin.
"There's no oversight on them, so I want to be part of that in my same critic and conscience role - but have more time to do it."
Health measures of New Zealand's lakes and rivers vary.
Under one criticised baseline adopted by the previous Government, 71.2 per cent of the country's lakes and rivers were currently "swimmable", while 68.6 per cent of rivers only were deemed safe for a swim.
One report out last month suggested river water quality around the country had seen a marked improvement in the last decade, while another recent government stocktake found levels of nitrate-nitrogen in monitored rivers were getting worse at more sites than were improving.
Levels of E. coli - a bacteria linked to animal or human faeces that can leave swimmers suffering vomiting, cramping, nausea and diarrhoea - weren't going up or down at most sites, but were significantly higher in the pastoral countryside.
Growing focus on the issue had led to one recent Colmar Brunton poll showing three quarters of Kiwis either very or extremely concerned about the pollution of rivers and lakes - and the topic was second to only housing issues.
Joy said that trying to spin the problem wasn't the solution.
"I think you can see with the election result that that's not what people want - they want the problem fixed."
Joy's criticism has in turn drawn its own - former Prime Minister Sir John Key dismissed his views on BBC's Hardtalk show and soil scientist and agribusiness commentator Dr Doug Edmeades implied he was biased, prompting a response from the New Zealand Association of Scientists.
The Critic and Conscience of Society Award's independent judging panel noted how Joy had made a substantial contribution over the past two years to raise public awareness of an important issue facing the country.
"He's single-handedly raised awareness of an issue that's at the heart of our country's primary economy and environment," panel member Professor Steve Weaver, of the University of Canterbury.
"While some of his messages are unpalatable to some, Mike has been a fearless crusader to ensure this issue remains a top of the agenda for central and local government, as well as for the agricultural industry."
Joy has previously received Forest & Bird's Old Blue award, the Ecology in Action award from the New Zealand Ecological Society, and the Royal Society of New Zealand's Charles Fleming Award for Environmental Achievement.