The New Caledonian IRD research institute says it didn't hide information about underwater dripstones as claimed by some activists.
Activists are against a Goro Nickel mining company plan to build a 21 kilometre long pipe that would dispose neutralised liquid mining waste into the lagoon at the Havannah Channel.
They say the pipe will go through an area of underwater stalagmites that have been discovered by the IRD in 2005, but were kept secret from the public.
An IRD spokesperson, Mina Vilayleck, says that's untrue.
"It's false, because the IRD has discovered this underwater stalagtite and has published it. There was a TV broadcasting and we have done some pictures and these pictures are online. So we've nothing to hide. We've published the discovery as soon as we were sure that it was a special geological site."