The sensitivity of contact angles in an aqueous environment to the surface energy of the solid is discussed. It is demonstrated that this sensitivity is much higher in an aqueous than in a vapor environment. The Girifalco-Good equation, in combination with the Owens-Wendt equation, is used for the approximate demonstrations. It is shown that the transition from complete wetting to complete dewetting by the aqueous phase in a solid-liquid-liquid system occurs over a much narrower range of the surface energy of the solid than in a solid-liquid-vapor system. It is also demonstrated that the contact angle may be extremely sensitive to small variations in the relationship between surface tensions and the corresponding interfacial tension.