Rapid CO₂ hydrate formation was investigated with the objective of producing a negatively buoyant CO₂−seawater mixture under high-pressure and low-temperature conditions, simulating direct CO₂ injection at intermediate ocean depths of 1.0−1.3 km. A coflow reactor was developed to maximize CO₂ hydrate production by injecting water droplets (e.g., ∼267 μm average diameter) from a capillary tube into liquid CO₂. The droplets were injected in the mixing zone of the reactor where CO₂ hydrate formed at the surface of the water droplets. The water-encased hydrate particles aggregated in the liquid CO₂, producing a paste-like composite containing CO₂ hydrate, liquid CO₂, and water phases. This composite was extruded into ambient water from the coflow reactor as a coherent cylindrical mass, approximately 6 mm in diameter, which broke into pieces 5−10 cm long. Both modeling and experiments demonstrated that conversion from liquid CO₂ to CO₂ hydrate increased with water flow rate, ambient pressure, and residence time and decreased with CO₂ flow rate. Increased mixing intensity, as expressed by the Reynolds number, enhanced the mass transfer and increased the conversion of liquid CO₂ into CO₂ hydrate. Using a plume model, we show that hydrate composite particles (for a CO₂ loading of 1000 kg/s and 0.25 hydrate conversion) will dissolve and sink through a total depth of 350 m. This suggests significantly better CO₂ dispersal and potentially reduced environmental impacts than would be possible by simply discharging positively buoyant liquid CO₂ droplets. Further studies are needed to address hydrate conversion efficiency, scale-up criteria, sequestration longevity, and impact on the ocean biota before in-situ production of sinking CO₂ hydrate composite can be applied to oceanic CO₂ storage and sequestration.