When a sound beam in water is incident on a sediment at a sufficiently small grazing angle, the resulting wave field in the sediment is complicated, even for the case of flat, fluidlike sediments. The wave field in the sediment for a sound beam from a simple transducer has an evanescent component and diffractive components. This situation has been experimentally simulated by using a combination of previously described immiscible liquids [Osterhoudt et al., J. Acoust. Soc. Am. 117, 2483 (2005)]. Measured wave-field features are similar to those seen in a wave-number-integration-based synthesis (using OASES) for a related problem. Targets are placed in the evanescent wave field to simulate scattering by targets buried in marine sediments. Features of the observed backscattering are relevant to detecting and clarifying objects in sediments. Measurements include the resonant excitation of the organ-pipe mode of open water-filled cylinders previously studied with free-field illumination [Osterhoudt and Marston, J. Acoust. Soc. Am. 113, 2334 (2003)]. The degradation of the backscattering with increasing target depth and with target tilt were measured and modeled. Simple approximate models of these properties are facilitated by the localized coupling processes for the excitation of (and radiation by) organ-pipe modes. [Work supported by ONR.]