Analyzing the diversity of marine algae and hermatypic corals of reefs and lagoons of New Caledonia, especially the south-east region of Grande Terre island called the forgotten coast. This region stretches from Thio to Ounia and is inaccessible by road. It stands out for its submerged barrier reef and lagoons which are highly influenced by the ocean. The region is classified in the Ecoregional analysis carried out by WWF and CRISP, amongst remarkable areas of New Caledonia which should be studied. These inventories will complement those undertaken in other regions of New Caledonia, particularly in the south west lagoon, reefs and lagoons in the north east and northwest in 2004, in the Loyalty Islands and Ile des Pins in 2005. Some groups have been studied in a phylogenetic and phylo-geographic study. In the long term, all these approaches will provide an analysis of the biodiversity on the scale of New Caledonia on the whole and highlight the characteristics of marine flora and coral reef fauna as well as biogeographical affinities on western Pacific and Indo-Pacific scales. The related programme is Biodiversity of tropical marine fauna and flora (IRD-UMR 7138 "Systematics, Adaptation, Evolution"). Comments on the cruise's progression: Sampling was originally planned at the Banc de la Torche located to the south of Ile des Pins, but these stations were abandoned due to weather. In addition, conditions at sea did not enable all the stations planned outside of the reef to be performed. But in spite of these setbacks, the different habitat types were sampled.