Coherent soft x-ray scattering experiments from a semiconductor sample consisting of InP islands on a smooth semiconductor substrate are described. The soft x-ray scattering was performed with 266 eV photons produced by an undulator source. Using a position sensitive detector, we are able to detect diffusely scattered x rays in the vicinity of the specular reflection, with an in-plane momentum transfer of up to 6 mu m(-1). Using Huygens-Fresnel theory and atomic force microscope images of the surface structure, we simulated the scattering assuming a finite lateral coherence length for the incident radiation. The lateral coherence length of the incident beam was found to be 20 mu m from a fit to the observed diffraction pattern from a pinhole. The effect of changes in the surface morphology on the speckle pattern was simulated to explore the potential of coherent soft x-ray scattering for the study of surface structure dynamics.