Ship design review (DR) involves extensive collaborative and participatory processes and requires all DR actors (designers, stakeholders, end-users) to manage a large complex decision space in addition to coping with heavy cognitive demands. Here, we present a novel system whose purpose is to optimize the balance between ship DR complexity and the users' cognitive effort. The system exploits the power of interactive multi-user immersive 3D environments based on efficient immersive Virtual Reality Mock-Ups (VRMU) obtained directly from 3D CAD models. The remote multi-user cooperative interaction is supported by tools like Oculus Rift and Oculus Touch, as well as by avatars to overcome geographic distance and increase social proximity. This will likely facilitate joined decision processes and, through enaction, the visualization of environmental features (error/feature detection, information search), thus promoting the project development towards success.