The past decade has witnessed a flourishing of different physical communication technologies for underwater wireless transmissions systems. Fast paced advances in optical, radio-frequency, or magneto-inductive signals technologies have ushered in a new era of multi-modal communication systems. In a nutshell, the majority of the systems seek to combine the short-range, high-bit rate of the new wave of technologies with the long-range, low-bit rate of the by now de facto acoustic communications solutions. This increasing flexibility opens a new realm of operations and solutions for underwater robotic vehicles working in cooperation. In this paper, we propose a new hybrid acoustic-optical under-water communication network for next-generation cooperative systems. We endeavor to describe its development in the scope of the EU Marine Robots Network project by a team, composed by the NATO STO Centre for Maritime Research and Experi-mentation (CMRE) and the Instituto Superior Tecnico of Lisbon (IST). In particular: the integration of the CMRE Cognitive-Communication Architecture (CCA) with the BlueRay optical modem of IST and its installation in marine robotic vehicles of the Medusa class. Laboratory and in-water tests using the Medusa stack and the Medusa class vehicles showcase the potentiality of the proposed network in future cooperative underwater missions.