This study investigated the effect of in-service training in the use of the ripple tank equipment on science teachers' pedagogical content knowledge (PCK) about the topic of waves. Three Grade 10 Physical Sciences teachers participated in this qualitative case study. The Refined Consensus Model informed the conceptual framework of this study, considering PCK at a topic level within each of the three realms of PCK. The training exposed teachers to the collective realm of PCK with the intention of developing their personal PCK about the topic. Teachers' personal PCK was explored by means of written Content Representations before as well as after the training. After the training, teachers' enacted PCK was observed and video-recorded while teaching the topic of waves to their learners. Pedagogical reasoning was elicited through video stimulated recall interviews. The post-training interviews also provided insight into participants' general views about the in-service training. The results show that the participants' personal PCK improved and that some of the content and skills taught during in-service training were utilized in the enacted PCK of two of the participants, particularly regarding conceptual teaching strategies. Least improvement occurred for the component of teachers' knowledge of learners' understanding. We found evidence that teachers' beliefs influence their pedagogical reasoning, acting as amplifiers and filters to translate newly acquired personal PCK into enacted PCK: teachers who prioritise hands-on experiences and teaching for understanding as opposed to rote learning are more receptive to training in the use of apparatus. The study therefore shows that training in the use of the ripple tank equipment improved in unique ways each of the teachers' PCK about waves.