As farmland shrinks, freshwater grows scarce, and climate patterns become increasingly unpredictable, humanity is looking seaward for answers. The ocean—vast, resilient, and largely untapped—is emerging as a new frontier for food security. This chapter invites readers to explore how ocean-based agriculture is transforming from a bold idea into a practical solution, blending science, ethics, and innovation. Imagine oceans not just as wild expanses, but as living farms. Picture intelligent seaweed cultivation guided by artificial intelligence, vertical farms anchored offshore, and underwater greenhouses like Nemo’s Garden that grow land crops beneath the waves using sunlight and stable microclimates. These aren’t science fiction—they’re real, and they’re reshaping how we think about growing food. We dive into the world of polyculture systems, especially Integrated Multi-Trophic Aquaculture (IMTA), where fish, shellfish, and seaweeds are farmed together in harmony. Each species plays a role—some feed, some filter, some absorb nutrients—creating a balanced ecosystem that boosts productivity and protects biodiversity. Through case studies—from Norway’s high-tech salmon farms to Zanzibar’s women-led seaweed cooperatives and the Faroe Islands’ climate-smart kelp initiatives—we see how ocean farming is already changing lives and landscapes. These stories show what’s possible when innovation meets local wisdom. Of course, ocean farming comes with challenges. We take a clear-eyed look at risks like pollution, disease spread, and habitat disruption. We also explore deeper questions: How do we ensure animal welfare? Who gets to benefit? How do we include communities in shaping this future? Policy plays a crucial role. We examine frameworks like India’s Blue Economy Strategy and the EU’s Ocean Multi-use Action Plan, which help guide sustainable investment and marine planning. On the tech horizon, we spotlight robotic aquaculture, solar-powered desalination, and multi-use ocean zones—all aligned with global goals like SDG 14 and climate resilience. This chapter ends with a call to action: to build ocean agriculture not just with cutting-edge tools, but with collaboration, fairness, and deep respect for marine life. The ocean can feed us—but only if we nurture it wisely.