The lack of research on ocean-related inquiry lessons and the desire to address local marine issues provided the impetus for this action research project in Newfoundland and Labrador. Teacher learning in this study is conceptualized as pedagogical content knowledge (PCK), which is framed using the Refined Consensus Model for PCK. Both teacher and student learning were examined during curriculum-based inquiry activities involving two ocean literacy principles (OLP): the ocean influences weather and climate, and the ocean and humans are inextricably interconnected. The 58 students in two classes co-taught by both authors participated in the action research study that was guided by two questions: What teacher PCK is developed during the preparation and enactment of inquiry-focused ocean education lessons? and How did our perceptions of student engagement and learning during ocean inquiry activities impact our PCK? Data sources included lesson plans, teacher reflections, and class field notes; 14 students consented to a review of their laboratory activity responses. Thematic analysis of data revealed that ocean inquiry lessons led to changes in teacher PCK while improving students’ ocean literacy.