Formic acid (FA), HCOOH, is the smallest carboxylic acid with pivotal roles in atmospheric, 1 prebiotic 2,3 and catalytic chemistry. Its interactions with water, both in the rarefied atmospheres of earth and on catalytic surfaces, can have profound effects on the resulting chemistry. FA is also important in astrochemistry, and was recently found to be present in interstellar ices, and can take part in the formation of amino acids such as glycine. To date there have been many studies, both experimental and theoretical, including quantum chemical calculations, aiming at understanding the mechanisms at play. Early work employed mass spectrometry to probe the thermodynamics and structure of FA clusters employing collision-induced ionization, electron impact and VUV photoionization. Very recently an electron impact ionization study of negatively and positively charged FA water clusters was reported coupled to theoretical calculations of the stability of neutral, cationic and anionic clusters. While some clusters were identified to be more stable, particularly in cyclic geometries, no systematic attempt was made to correlate the stability of these clusters with that of the appearance of magic numbers in the mass spectra as the emphasis of the study was to identify the distribution of neutral FA water clusters. The consensus that emerged, is that for FA clusters with water, open chain structures with water bound to the end are favored for n<4, while the hydronium ion acts as a nucleation site beyond n = 4, and the open chains tend to take cyclic structures. FA pentamer with hydronium ion has been implicated as a magic number as observed in different mass spectrometry experiments, and theoretical calculations suggest that the hydronium is located at the center of a ring composed of five FA molecules. Beyond stabilizing certain magic structures, water clusters can also play a catalytic role in the dehydration and decarboxylation of FA, presumably via cis-trans isomerization dynamics, where the cis isomer leads to decarboxylation and the trans isomer follows the dehydration pathway.