Self-Contained Underwater Breathing Apparatus (SCUBA) diving is always regarded as a risky activity to be conducted as an extra-curricular activity in the schools of Hong Kong. However, it provides a golden opportunity for students to experience the marine nature and serves as an excellent pedagogical tool of field based learning on the environmental education. The presentation will report a case study of an international school in Hong Kong on how they utilize SCUBA diving as a tool to enhance their students' knowledge about ocean and to foster the pro-environmental attitude. The teachers of the school have developed a tailor-made curriculum using problem-based approach, articulating with the discussion of current local environmental issues on marine conservation. The students have been forming a team to join the annual global citizen-scientist programme, Reef Check, to contribute their effort in revealing the health of coral community system in Hong Kong. A mixed research method, which includes semi-structured interviews of teachers, current students and alumni, and the self-administered questionnaire for them, was adopted in the study to evaluate the ocean literacy and pro-environmental attitude of the students and the effectiveness of the programme. The difficulties faced by both the teachers and the students throughout the implementation period of the programme will be reported. The opportunity and the challenge to run such a programme in the local school will be discussed, which would provide significant insights to other local schools conducting similar field-based learning and teaching activities.