The first goal in this challenge was to identify a number of vibrationally well-characterised, diverse monohydrate complexes of small organic molecules in the existing experimental literature, for which the lowest energy structure involves water as the hydrogen bond donor and thus Further mandatory entries of every submission included the proposing researcher and institution (not necessarily from the group publishing the experimental data) as well as the spectroscopic detection, wavenumber calibration, and cooling techniques used. Concerning the observed wavenumber, the submitter had to estimate its accuracy, to predict the relevant docking site for the observed water molecule and to assess whether the monohydrate was the global minimum arrangement of the two complex partners.