Coral reefs, a major source of marine tourism, are under threat worldwide due to human activities. There is an urgent need for information that could be used to promote efficient marine park management. In this study the economic benefits associated with scuba diving in Mu Ko Similan Marine National Park, Thailand, is estimated using a single- and double-bounded dichotomous choice contingent valuation survey design. The results indicate that divers are willing to pay about US$27.07–62.64 per person per annum on average, resulting in aggregate benefits of between US$932,940 and US$2.1 million per annum. The present value of these aggregate benefits ranges between US$31 and US$71 million, using a social discount rate of 3%. The policy implications for park management are discussed.