Oceans offer good opportunities for sustainable economic development. More and more, energy, fisheries and transport infrastructures are being established offshore. However, this growing demand for maritime transport, resource extraction, offshore energy, fisheries and aquaculture, is threatening marine ecosystems and sustainable maritime activities. H2OCEAN is a project aimed at developing an innovative design for an economically and environmentally sustainable multi-use open-sea platform. Wind and wave power will be harvested and part of the energy will be used for multiple applications on-site, including the conversion of energy into hydrogen that can be stored and shipped to shore as green energy carrier and a multi-trophic aquaculture farm.