We have observed several heterodimers displaying hydrogen bonding to a sulfur atom. The larger atomic size, smaller electronegativity and high polarizability of sulfur compared to oxygen changes the hydrogen bonding properties. As an example, a comparison of four monohydrates involving bonding of furfuryl acohol, furfuryl mercaptan, thenyl alcohol and thenyl mercaptan with a single water molecule serves to illustrates the hydrogen bond differences when replacing one or two oxygen atoms by sulfur. In terestingly, in the two mercaptans water retains internal mobility in the cluster, as tunneling doublings in the spectrum confirm an internal rotation motion of water in the dimer.