The main aim of this study was to examine how a group of elementary students perceived their engagement in a project-based science intervention investigating the water quality of a local lake. The students collaborated with a scientist to conduct various experiments and used handheld computers to collect and analyze data in order to examine the quality of the water. The unique aspects of this intervention were the nature of the task (i.e., study of a real-world, local, problem) and the use of handheld computers for data collection. An urban, fifth-grade, European elementary school classroom defined the context of this study. The research data consisted of classroom observations, videos of the students engaging in activities in the classroom and outdoors, interviews with the students and the teacher, students' presentations, various worksheets and assessment materials. Data analysis illustrated that students perceived certain aspects of the intervention as significant: the collaboration with the scientist, the nature and context of the activities, and the use of handheld computers. This finding has implications about the value of engaging students in project-based science activities and using mobile technologies to support these activities and enhance students' interest.