Blue finance channels capital toward ocean conservation and sustainable maritime industries. This chapter asks whether blue bonds and debt-for-blue swaps can simultaneously protect marine ecosystems and bolster the fiscal resilience of coastal states. Surveying recent issuances in the US, China, and other jurisdictions, we map design choices—use-of-proceeds covenants, impact reporting, and concessional pricing—that determine environmental credibility and investor appeal. Evidence shows that well-structured blue bonds mobilize resources for biodiversity protection, pollution abatement, and fisheries governance while lowering borrowing costs for heavily indebted nations. The Seychelles and Belize swaps converted sovereign liabilities into long-term funding for marine protected areas, illustrating a debt-relief channel absent from conventional green finance. Yet the market remains vulnerable to greenwashing (or “bluewashing”), uneven taxonomies, and lax verification dilute impact. Three policy lessons follow. First, harmonized global standards and third-party auditing are essential to ensure genuine progress of sustainability. Second, high-debt coastal economies should integrate blue instruments into their debt-management strategies to unlock concessional capital. Third, cross-sector collaboration—linking governments, development lenders, private investors, and local communities—maximizes ecological returns and generates shared economic benefits.