Synchrotron X-ray reflectivity is used to study the electron density profile normal to the interface between bulk water and bulk n-docosane (C22H46), These measurements are interpreted in terms of an error function electron density profile to yield an interfacial width of 5.7 +/- 0.2 Angstrom. In contrast with an earlier measurement on the water-hexane interface, this interfacial width disagrees sharply with the prediction from capillary wave theory, sigma(cap) = 3.5 Angstrom. This width can be accounted for by combining the capillary wave prediction with a contribution from intrinsic structure due to the bulk correlation length of docosane, We also discuss the absence of interfacial freezing at this interface, a phenomenon observed fur n-alkanes of a similar chain length at the alkane-vapor and alkane-silicon oxide interfaces.