“Ha’u Nia Tasi, Ha’u Nia Timor” (My Sea, My Timor): A Mixed-Methods Investigation of Marine Tourism and the Blue Economy in Timor-Leste

Small island states often promote tourism as a development solution, yet weak governance and unequal political–economic structures frequently allow benefits to leak offshore while environmental costs are borne locally. In Timor-Leste, this risk is acute as the economy confronts the imminent loss of oil and gas revenues following the closure of the Bayu-Undan field in 2025. Despite the prominence of tourism in national policy, policymakers lack concrete evidence on whether marine tourism can deliver high-value growth without undermining fragile marine ecosystems or customary governance systems. This study assesses economic opportunity, marine biodiversity, and conservation effectiveness for marine tourism in Timor-Leste, and it compares ecological outcomes across protected and unprotected sites. Our methods combine ecological surveys, exit-survey economics, and stakeholder interviews. The data collection includes biological observations from four Ataúro Island sites (5, 308 individual taxa; 118 fish species) and a purpose-built international passenger survey of 238 visitors conducted at Dili Airport in July 2024, providing current and activity-specific spending data. Marine tourism is found to deliver high economic returns, with SCUBA divers spending an average of US1, 600 over 10 nights, and 90% reporting complete satisfaction. By 2035, forecasts suggest that diving, snorkelling, and whale watching could generate an estimated US60. 64 million (approximately 44% of leisure visitor spending) in an optimistic scenario, or around US33. 00 million (38% of leisure visitor spending) under more conservative estimates. Community-managed Tara Bandu sites exhibit significantly higher predator abundance and far lower coral damage than unmanaged sites (8% versus 27%). The results demonstrate that marine tourism can underpin the country’s economic diversification; however, it must be accompanied by strengthened governance, community authority, the enforcement of spatial protection, and the alignment of investments with ecological sustainability.