Fale oceaniczne: doskonały przykład układu złożonego [Ocean waves: the perfect example of a complex system] Frederic Dias (School of Mathematics and Statistics, University College Dublin, IRL) Scales in ocean waves range from the molecule size (of the order of the nanometre) to the size of the earth (several thousands of kilometres). In this talk, we will explore the complexity of this wide range of waves. We will describe the scientific challenges associated with the study of ocean waves and how a multidisciplinary approach is often the only way to move forward. Ocean waves can be both beneficial to society and damaging to infrastructures when they become highly energetic. We will focus on two particular topics: (i) Extracting the energy of ocean waves: why has it mostly failed so far? and (ii) Building our own wave observation station in a remote area on the west coast of Ireland: how involving the local community has played a vital role in shaping the success of the station.