Difference between water solubilities of phenol and cyclohexanol?
In addition to the acidity difference described in the comments, there is a more subtle effect involving conjugation in the undissociated phenol.  When the phenyl group withdraws some electron density from the π-donating hydroxyl group, it gains some negative charge and so is better able to attract the hydrogen ends of the water dipoles.  Ultimately this is a manifestation of the polarizability of the delocalized π electrons.