With the growing adoption of IT in tourism, mobile games are becoming an attractive interpretive tool, particularly in heritage contexts where a deeper appreciation for the heritage attraction may serve to safeguard it into the future. This study adopts a user-centred approach to systematically explore the process of developing a serious game as an interpretive tool for the Great Barrier Reef, Australia. The study uses a gaming conceptual framework, the Design-Play-Experience (DPE) model and data were collected in situ, on reef tours, by observing respondents’ interactions with the game, video recording and reviewing their gameplay and through pre and post interviews with respondents until data saturation was reached (n = 34). The findings illustrate how games can be designed to represent a complex and threatened ecosystem and elicit positive emotions among tourists, particularly curiosity and delight. The study illustrates the usefulness of the DPE framework to move beyond a simple description of games to a systematic, user-centred analysis of the process of creating a serious game to solve a particular interpretive problem. The study also confirms that designing a bespoke game for a tourist attraction is a costly and difficult process, requiring iterations of the game design, that is arguably outside the scope of many nature-based/heritage tourism businesses.