Coherent diffractive imaging using x-ray free-electron lasers (XFELs) may 
provide a unique opportunity for high-resolution structural analysis of single 
particles sprayed from an aqueous solution into the laser beam. As a result, 
diffraction images are measured from randomly oriented objects covered by a 
water layer. We analyze theoretically how the thickness of the covering water 
layer influences the structural and orientational information contained in the 
recorded diffraction images. This study has implications for planned experiments 
on single-particle imaging with XFELs.