The article illustrates the implementation of an interdisciplinary unit "Maths to save the sea", originally used in a Year 8 classroom in Queensland and later modified to include essential learnings rather than outcomes. The unit integrates literacy and numeracy, interdisciplinarity, middle years' signifying practices, and concepts of authentic and productive assessment. Implementation of the unit assesses what students would know, the value of that knowledge, and how assessment would achieve positive learning outcomes.