The app 'Roteiro Entre-Marés' offers digital itineraries for exploring intertidal zones, such as the rocky platform of the Avencas Marine Protected Area. As users travel through the intertidal area, several challenges emphasising the biodiversity and environmental issues are presented. Eighth-grade students (n=63) used this application and were challenged to identify "in situ" the marine species present in different zones of the intertidal ecosystem. Then, questionnaires and interviews were performed with teachers and students to examine the utilisation of mobile apps as educational tools. The fact that they learnt a lot, autonomously, using the field guide of the app, was among the aspects that the students most appreciated, describing this app as an organised, informative, interesting, and interactive learning tool. Teachers say this is a useful didactic resource because it delivers clear and reliable information that links theory and practice. Hence, this study examines the acceptance of this mobile app as an instructional tool among students and teachers, highlighting the potential of mobile apps as educational tools.