<![CDATA[Water Quality Management is an essential competency in Brackish and Marine Fisheries Agribusiness because it requires students to integrate scientific knowledge, technology, quantitative analysis, and problem-solving skills in authentic aquaculture contexts. However, learning activities are still predominantly supported by conventional materials, while the use of digital learning resources remains limited. This study aimed to develop a STEM-based e-module for Water Quality Management and determine its validity, practicality, and effectiveness as a learning resource for vocational high school students. This study employed a Research and Development (R&D) approach using the ADDIE model, consisting of Analysis, Design, Development, Implementation, and Evaluation. The participants were 15 eleventh-grade students of the Brackish and Marine Fisheries Agribusiness Program and one subject teacher at SMK Negeri 1 Seri Kuala Lobam. Data were collected through expert validation sheets, teacher and student response questionnaires, and pretest–posttest assessments. The results showed that the e-module was highly valid and highly practical, with validation and practicality scores of 93.75% and 98.6%, respectively. Learning outcomes improved from a mean pretest score of 73.0 to 90.0, with an N-Gain of 0.61, categorized as moderate. The t-test indicated a significant difference between pretest and posttest scores (p < 0.05). These findings indicate that the STEM-based e-module is a valid, practical, and effective digital learning resource for Water Quality Management in vocational fisheries education]]>
