A simple model, in which deposition is limited by diffusion through a thin laminar film of water, has successfully described the deposition of several gases to the sea. However, the deposition velocity of ozone to seawater is 10--30 times greater than this model predicts. This enhancement is attributed to significant reactions of ozone with halides and other components of seawater within the laminar surface layer, and a modified version of the model for ozone, and possibly other reactive gases, is proposed. To test the model, comparisions were made of predicted and observed deposition velocities for ozone to solutions of sodium sulphite and nitrite. Measurements of the rate constants for the reaction of ozone with these solutions and with some components of seawater were made with a stopped flow apparatus. The reaction with iodide was too rapid for direct observation, but the rate constant was inferred from measurements of the deposition of ozone to iodide solutions. According to the model, iodide makes a substantial contribution to the deposition of ozone to seawater, but an additional, unidentified reaction is necessary to explain fully the deposition rate. A surfactant species may well be involved. The model indicates that the ozone is destroyed and the oxidation products produced in the top few microns of the sea. The production of molecular iodine at the surface may have significant geochemical consequences.