The Sea Urchin in the Room is a project that explores how a designed learning experience can bring up the issue of acidification in the ocean in creative ways. Emerging from the fact that it is hard to actively relate to what is happening with an ecological system that is distanced to us the project aims to create new inspiring levels of engagement to life under the surface. The learning experience is informal and put emphasis on learning by doing for best remembering what was experienced. It offers the conditions of learning about an ecological issue by actively involve the non-scientific public. When knowing more about the issues, sustainable attitudes can be inspired. The project zoom in to one specific species that gets to be the ambassador of the acidification, namely the sea urchin. The outline of the practically researched-based project is an enlarged sea urchin that stands in a public space for two days. The scale of the sea urchin challenges our perspectives to arrive at new ones.