In this paper, a self-created analogy is presented based on comparing the process of osmosis with a situation recreated in a train carriage. It was implemented with upper-secondary education students at a secondary school in Chiclana de la Frontera (Cádiz, Spain). To assess the progression of the students' models on osmosis, their activities during the implementation were used. Their perceptions of the analogy and the strategy used were analysed from their answers to a questionnaire using Likert-type and open questions. A qualitative and quantitative analysis was carried out. The results show that the analogy helps the initial models of osmosis advance towards more complex models. The students value the analogy positively. They explain it helped them develop scientific skills and attitudes like teamwork. It is concluded that the analogy designed is a valuable tool to bring students closer to the concept of osmosis, although it needs to be integrated into teaching-learning sequences.