Blind challenges in the field of computational chemistry have become more and more popular over the past years. Particularly noteworthy examples thereof are the Statistical Assessment of Modeling of Proteins and Ligands (SAMPL) challenges initiatives and the Cambridge crystallographic database structure challenges. This is followed in smaller scale by individual groups initiatives, or even in structured round-robin tests. Whatever the case may be, these challenges provide unique opportunities to pit different methods to the same observable in a collegiate (optimally unbiased) fashion. A previous challenge promoted by some of the groups involved was the furan-methanol challenge, whereby the binding preferences of methanol and a series of modified furan molecules was under scope. The question posed to the theoretical groups was to identify the most stable binding motif, an OH• • • O or OH• • • π bound conformer. Although the experimental data for the challenge were jet-cooled vibrational spectra, the target quantities were energy differences. The latter were estimated from the relative heights of the observed absorption peaks for the different binding modes. Albeit this being an indirect measurement, conservative error estimates were still below 1 kJ/mol, well beyond the error bar of commonly accepted theory benchmarks. In this new joint effort, the observable to be tested is no longer inferred from the spectra. The goal is to correctly predict the experimental red shift of the OH bond stretch in 1:1 monohydrate complexes relative to the free symmetric stretch. This builds a much more rigorous connection point between theory and experiment in the important field of microhydration , as a quantity that both sides of the table feel comfortable estimating with minimal modelling on the experimental side. With its sensitivity to both electronic structure and nuclear motion aspects , it promises interesting error cancellation and thus Pauling point situations. As monohydrates are vibrationally far less characterised than rotationally , the topic also leaves enough playground for blind testing. As the layout of this blind test has been described extensively before, we refrain from repeating the experimental tools and caveats. As detailed in our first publication introducing the challenge , a set of 10 hydrate systems were selected as 'training set', in order for the participants to fine tune or validate beforehand their approaches. The latter consisted of: acetone (ACE), acetophenone (APH), 1,2,4,5-tetrafluorobenzene (TFB), 1-phenylethanol (POH), imidazole (IMZ), aniline (ANL), dibenzofuran (DBZ), di-tert-butyl nitroxide (DBN), o-cyanophenol (OCP) and cyclobutanone (CBU). Another set of 10 structures was chosen and presented as the target of the challenge -from now on referred to as 'test set'. The latter consisted of: cyclooctanone (CON), 1,3-dimethyl-2-imidazolidinone (DMI), formaldehyde (FAH), methyl lactate (MLA), 1-phenylcyclohexane-cis-1,2diol (PCD), pyridine (PYR), tetrahydrofuran (THF), tetrahydroth-iophene (THT), 2,2,2-trifluoroacetophenone (TPH) and 2,2,2trifluoroethan-1-ol (TFE), all previously uncharacterised in terms of the experimental water stretching vibrations in the vacuumisolated complex. The participants were given 6 months between the test set reveal and a submission deadline. Following said deadline, any inconsistencies in the submissions were addressed. One issue we had to address was the use of different levels of theory within a single submission (i.e., higher levels of theory for the smaller systems, computationally cheaper approaches for the larger cases). Our solution was in general to ask the participants to split the data into different sets. This was done to increase the amount of information about the different levels of theory featured, while ensuring a strict unique procedure (level of theory) per computational data set. There were also some issues with the definition of the reference -the symmetric water OH stretch. This was the only value which we allowed to be revised. Otherwise, all of the data was kept as submitted, even including mistakes in the molecular structure. Issues in the individual submissions are later noted in the text. As previously discussed, the training and test sets covered roughly the same range of wavenumber downshifts, from a very low (10 and 8 cm -1 for TFB and TFE respectively) to a rather high end (199 and 203 cm -1 for IMZ and PYR respectively). Fig. provides the Lewis structure of the compounds selected for both sets, as well as the experimentally obtained absolute position of the water OH donor stretch bands.