In this article, 61 high-school students learned about ocean acidification through a virtual laboratory followed by a virtual lecture and an asynchronous discussion with a marine scientist on an online platform: VoiceThread. This study focuses on the students' development of ocean literacy when prompted to ask questions to the scientist. The students' questions were thematically analysed to assess (1) the kind of reasoning that can be discerned as premises of the students' questions and (2) what possibilities for enhancing ocean literacy emerge in this instructional activity. The results show how interacting with a scientist gives the students an entry point to the world of natural sciences with its complexity, uncertainty and choices that go beyond the idealised form in which natural sciences often are presented in school. This activity offers an affordable way of bringing marine science to school by providing extensive expertise from a marine scientist. Students get a chance to mobilise their pre-existing knowledge in the field of marine science. The holistic expertise of the marine scientist allows students to explore and reason around a very wide range of ideas and aspect of natural sciences that goes beyond the range offered by the school settings.