This study investigated sixth-grade students' development of multidisciplinary models involving the integration of mathematics, science, and statistics, together with shared STEM practices. Mathematics and science featured a reciprocal relationship within the real-world context of tsunami inundation. Experimenting with water tubs comprising "landmasses" and "shore slopes" of varying angles, students explored how varying the slope of the shoreline affects the inundation distance. Given that organising and structuring data are essential to the creation of models as systems of representation, students' modelling revealed a basic understanding of key statistical concepts and processes, including variation and covariation, and an ability to identify trends both within and across data sets. Students were able to apply their learning in recommending ways of minimising the impact of a real-world tsunami, demonstrating how such an investigation can facilitate understanding of natural phenomena. The overall findings indicate how elementary-grade students can successfully engage in independent multidisciplinary modelling within integrated STEM investigations and develop important conceptual understandings in the process.