Marine conservationist and diving guru Wade Doak described the volume of rubbish as "colossal".
"Everyone talks about the impact on fish, and whales, but what they don't realise is that microscopic particles of plastics are going back up the food chain, and into our own diets."
He said responsibility came back to individuals, who were still deciding to use plastic items, when alternatives were available.
His granddaughter snorkelled this week, he said, and saw more plastic than fish.
A tax on plastic items and a subsidy on organic materials could encourage a reduction in plastic use.
Last year, the Sea Cleaners crew cleaned up more than 31,500 litres around Whangarei's Hatea River, and 5000 litres from Ruawai in eight hours.
More rubbish was cleared at Ruakaka, One Tree Point and Marsden, Tutukaka, Ocean Beach, Urititi, Whangarei Heads and in the Bay of Islands.
Most of the work focused on the east coast of Northland, where the population mass was found.
From plastic bottles in mangroves, tractor and truck tyres, and TV sets in the Town Basin, scores of Sea Cleaners' volunteers pulled 88,900 litres of rubbish (about 711,200 items) out of the water from October 20 to December 22 last year.
In that three month period, volunteers from all walks of life collected from beaches, bays, and upper harbours with about 90 per cent of the waste washing out to sea from the stormwater systems.
The remaining 10 per cent came from commercial and recreational fishing.
The organisation gave a presentation to Whangarei District Council on Thursday about its need for a further $150,000 so it can expand its work, which costs $25,000 each month.
Hayden Smith, who started the initiative in Auckland, before expanding to Northland, said the funding allowed the team to staff, maintain and operate its three boats.
One boat had been donated by Whangarei businessman, Tony Davies-Colley, and Sea Cleaners had two more in Auckland.
"We are finding everything from plastic bottles to bait bags and fishing lines," said Mr Smith.
The teams were also finding the plastic soy sauce containers that accompany sushi.
"The fish nibble these, and that's not good."
They collected 40,000 litres of rubbish in 2014, during a one-month trial.
In 2015, a three-month stint cleared 80,000 litres, and the same was cleaned up last year.
A Sea Cleaners' audit counted about eight items per litre bucket, meaning the team has collected more than 1.6 million items since it started.
"It's the same amount each time, which tells us that we should be doing more than just a spring clean - we need to work all year round."
The volunteers use the boat to get to hard-to-reach spots, before going ashore to tackle the high tide line.
"We have done some diving but it's mostly on foot."
With just enough funding for six months' work, Smith and the team need a further $150,000 for the Northland work.
The rubbish is brought to Northland Waste's centre in Whangarei at no cost.
Marsden Cove Marina also provided waste disposal options for the crew.
Mr Smith told the Advocate that these were critical support structures for the team.
He urged people wanting to help to pick up rubbish inland as "this will end up in the waterways".
"We're not sure when we will start work in 2017 but this year, we can afford a six month clean-up," he said.
