This article examines a 15 year-old master level seminar dedicated to the exploration of local and complex environmental issues marked by scientific or technological uncertainties. Following a pragmatic learning approach, we focus our discussion on a triadic relationship between supervisors, students and various concerned publics. A local flood management controversy in Belgium will help to illustrate our approach and point to some learning outcomes. On the basis of this pedagogical experience, we propose to shift from Problem-based-learning towards "Public"-based-learning that rests on the comparison of the various ways a problem is defined by publics. This comparative approach allows us to deduce a plurality of modes of involvement mobilized in the management of the environmental problems.