<p>Water’s anomalous properties, such as its density maximum and high surface tension, are emergent phenomena originating from its molecular-scale behavior. This review charts a journey through water clusters, from the simple monomer and dimer to complex three-dimensional aggregates, to illuminate how hydrogen bonding evolves from a pairwise interaction into a cooperative, multi-body network. We highlight how this progression reveals the critical role of molecular undercoordination, which drives a unique electronic restructuring at surfaces and interfaces. Frameworks such as Bond Order-Length-Strength (BOLS) and Hydrogen Bond Cooperativity (HBCP) provide a consistent picture that re-focuses the explanation from molecule-proton motion to bond-electron dynamics, suggesting a connection between cluster behavior and the distinctive properties of bulk water.</p>