Seaboost (Groupe Egis) and XtreeE have combined their unique skills in ecological engineering and large-scale 3D printing to design, manufacture and immerse the first reef of a new generation. The 3D concrete printing technology developed by XtreeE made it possible to recreate an unprecedented porous architectural complexity mimicking one of the richest natural habitats in the Mediterranean and difficult to recreate: the Coralligenous. This deep rocky ecosystem of biogenic origin can take several hundred years to form and then house several thousand species (fish, crustaceans, corals, algae, molluscs etc). In a global context of degradation of the marine environment, 3D concrete printing offers unlimited prospects for future engineering and ecological restoration projects from Mediterranean waters to the Great Barrier Reef in Australia.