Implementing Artificial Reefs (AR) is seen as a worldwide strategy to overcome the problematic environmental impacts due to climate change, overfishing and other activities that damage natural habitats and ecosystems. The production and deployment of ARs involve a series of technical challenges and this work explores a possible alternative solution to overcome some of these challenges. This work addresses a new system for building underwater modular structures integrating monitoring sensors, exploring the potential that Flat Knitted textiles have when specifically designed and used as Knitted Textile Preforms (KTPs) for concrete filling. The casting of AR modules directly in their final position, underwater, brings new paradigms to the design and production of ARs clusters with more complex geometries and geometrical continuity between modules. This manuscript is dedicated to the analysis of variables such as injection pressure and its variations during filling and curing, respectively, as well as the textile structure and geometrical design. It also addresses the possibilities of the technology to embed environmental sensors, which will add functions to the AR structure.