A theory of capillary-gravitational waves in the transition region between seawater and liquid carbon dioxide in deep oceans is proposed. It is shown that the thickness of the transition layer affects the properties of capillary-gravity waves. The question of the structure and stability of wave disturbances at the interface between seawater and liquefied carbon dioxide is essential for the safe storage of liquefied carbon dioxide in the ocean. This is an important issue on the current agenda in light of global warming.