The MORPH project (FP 7, 2012-2016) aims at the development of efficient methods and tools to map the underwater environment in situations that defy existing technology. Namely, missions that involve underwater surveying and marine habitat mapping of rugged terrain and structures with full 3D complexity, including near-vertical cliffs. Potential applications include the study of cold water coral reefs or ecosystems in underwater canyons. For mapping purposes, the project advances the novel concept of an underwater robotic sensor carrier consisting of a number of spatially separated mobile robotic modules, each of them carrying complementary sensors. The modules are connected virtually via wireless communication links. Free from the constraints of rigid links, the modules can reconfigure themselves spatially and position their sensors optimally as a function of the shape of the terrain, which may include walls with a negative slope. In the scope of the project, a final demonstration on a vertical cliff will validate the efficacy of the methods developed.