The protesters insist the plan threatens a "unique" natural habitat.
"The Amazon reef is not an oil well" and "Defend the Amazon reef," read banners held aloft by supporters of Greenpeace and environmental group ANV-Cop21 as they converged on some 30 towns including Paris, Rennes in the west, Bordeaux in the south, and Nancy in the east.
At the stylish early nineteenth century Lions de Nubie fountain in Paris' La Villette district, some protesters daubed themselves with molasses, waded into the water and smeared the sticky black goo on the structure.
"Total insists on going after oil when there are ecosystems and jewels of [ecological] diversity to preserve. It's no longer the age of oil but of transition" to cleaner forms of energy, Greenpeace campaigner Edina Ifticene told AFP.
The protests came as Total was preparing to unveil the findings of a new study into the planned project's impact to Brazilian authorities.
Greenpeace has documented the existence of coral in the target area.
In late May, Brazil's environmental agency Ibama urged Total to look deeper into the consequences of drilling, judging its initial study "insufficient."
"We have four months to respond. We are being asked to undertake extra studies and we shall do so," Total chairman Patrick Pouyanne said at the time, insisting the company would ensure the plan respects the environment.
At the same time, the company rejected as "non-existent" the risks highlighted by opponents.
Greenpeace says the coral reef, discovered in 2016 - some three years after Total bought exploration blocks just a handful of kilometers away, is larger than first thought and extends into the area where Total wants to drill.
It is concerned of the effects of a potential oil spill on the ecosystem and nearby coastal mangrove.
"We have to stop this abuse. The oil firm should not drill near this ecosystem and near this mangrove which, if touched by an oil slick would be impossible to clean up," insisted Ifticene.
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