This chapter delineates the rationale, scope, and structure of this book. Cruise tourism sustainability is approached as a complex, systemic challenge, likened to the mythological Hydra, requiring multi-dimensional, coordinated responses. While the sector’s environmental impacts have drawn the most attention, a holistic sustainability paradigm calls for a consideration of the corresponding economic and social dimensions, whose interdependencies often produce unintended consequences. Singular solutions, such as alternative fuels or cruise bans, can exacerbate other issues, unless they are integrated into broader systemic frameworks. The authors argue that effective sustainability in cruise tourism demands a paradigm shift: from isolated measures and reactive compliance to long-term, strategic collaboration across stakeholders. Through this lens, cruise tourism is not inherently unsustainable; its transformation toward a regenerative model calls for innovation, transparency, and adaptive governance.