"I was very concerned for our health," she said.
The last dive, 11 years after the Rainbow Warrior was scuttled on to the sandy sea floor, left her shocked by the rate of deterioration. The inside of the ship had collapsed and the outside of the hull was covered in dust.
"We couldn't see the sea life and the whole image was grey and desolate, with very little fish."
Ms Middleton said it seemed as if nothing happened for about seven years and then it all broke down at once rather than gradually over time.
She said if the Rena disintegrated like the Rainbow Warrior, it would kill the sea life. That was when the disaster would show its full effects from heavy-metal poisoning.
"It may appear to be okay at the moment after four years, but it is year seven onwards that worries me."
Ms Middleton, who has done 40 dives on Astrolabe, also feared the hull may attract species of plants that were tolerant to the paint and high iron content of the wreck, instead of the normal dominant plant species in the area.
"The reef may appear to be healthy but in fact it could be dying because of the more aggressive iron/spray dominating species surviving and becoming a weed ... we need to put saving the environment over economics and fully remove the Rena."
Debbie McCauley, author of the award-winning children's book, Motiti Blue and the Oil Spill, said the owners and insurers of the Rena must face the consequences of their actions.
She said Rena rubbish was present in the seven sacks of rubbish collected by the Mauao Area Wildlife Trust last weekend. Container insulation showed that the wreck was still producing little "gifts" for the community to deal with.
"Our community doesn't want potential environmental effects managed, we want nil possibility of future environmental effects. My message is simple, stop muddying the waters and remove the wreck," she said.
Eric Gosse, a commercial diver and mariner, said the Rainbow Warrior deteriorated because it was cheaply built of recycled steel. This applied to a degree to the Rena.
As with the wreck of the SS Wiltshire off Great Barrier Island, the Rena was likely to end up with its upper plates largely lying over each other. "This will not prevent it providing homes for the small fish that Astrolabe lacked."
Why Tauranga children's book author Debbie McCauley wants the Rena gone
"If you make a mess in someone else's home, you clean it up."
"Insurance and shipping companies are trying to dodge their responsibilities."
"Do what is morally right so we can all move on."
