Knowledge of the scientific study of the sea in the early twentieth century is essential to understand the process through which marine biology was institutionalised in Portugal. The first national biological stations were set up during the First Republic: the Estação de Zoologia Marítima da Foz in Porto, and the Aquário Vasco da Gama in Lisbon. This paper is a case study on the Estação da Foz, which played an important role by assisting the Zoology Institute at the Universidade do Porto in achieving its strategic objectives, and provides an understanding of the institutionalisation process for marine biology within a university context: its connection with teaching, research, the economy, and society.