Seawater samples were collected using a technique that isolated the upper 0.15 mm of surface water. Much of their organic matter was surface‐active, slick‐forming material that was originally at the seawater‐air interface. These surface‐active molecules are of interest because of their influence on many properties of the sea surface. Determinations were made of the effect of monolayers of these materials on the surface tension, on the surface potential, on the damping of capillary waves, and on the surface viscosity. The measurements were made as functions of the area of surface occupied by the adsorbed molecules. Organic materials collected from widely different locations were surprisingly similar in their behavior, suggesting that the more strongly adsorbed, stable, film‐forming materials at the interface were chemically similar. It is suggested that the more stable components of the films are primarily polar‐nonpolar compounds containing long‐chain hydrocarbon groups, such as the high molecular weight saturated and unsaturated fatty acids and their esters.