This book comprises the proceedings of the 12th International Conference on Asian and Pacific Coasts (APAC), held in Busan, South Korea on November 4–7, 2025, which was supported by the Korean Society of Coastal and Ocean Engineers (KSCOE), the Chinese Ocean Engineering Society (COES), and the Coastal Engineering Committee of the Japan Society of Civil Engineers (JSCE). It covers topics such as coastal waves, nearshore currents and sediment transport, coastal structures, coastal morphology and beach nourishment, natural hazards, coastal management, and renewable energies. Written by leading researchers and engineers, and selected by means of a rigorous international peer-review process, the contributions highlight numerous exciting ideas that will spur novel research directions and foster multidisciplinary collaborations.