This paper summarizes the main activities conducted to design, optimize and build a prototype of an innovative light amphibian. This aircraft is a “PrandtlPlane”, a particular box-wing configuration which introduces relevant advantages as increased aerodynamic efficiency and safety of flight; the research project, called IDINTOS, has been co-funded by the Regional Government of Tuscany (Italy), coordinated by the University of Pisa and carried out in 30 months by a consortium of public bodies and small private firms, starting from 2011. In this contribution an overview is given also on several aspects concerning the design, as the aerodynamic optimization, the construction and tests of three scaled models for towing tank wind tunnel and, flight tests, respectively.