Nature-based tourism experiences have the potential to change the environmental knowledge, attitudes and behavior of visitors; but such experiences may be beyond the physical and/or financial reach of many people. To influence the conservation behavior of populations world-wide, a more accessible yet equally effective strategy is required. Using an experimental design, this study explored whether a conservation documentary about Australian marine environments, together with post-viewing support materials, prompted the adoption of conservation behaviours. Questionnaires revealed environmental knowledge, attitudes and behavioural intentions rose immediately after viewing the documentary. Ten weeks later, these levels were maintained or decreased slightly for those who received post-viewing support (Facebook, help sheet or both), but decreased markedly in the control group. Results are similar to those reported in wildlife tourism studies. Implications for the use of documentaries in place of nature experiences are discussed.