The optimization work conducted herein builds on a multi-reference particle swarm optimization software that we developed recently: Swarm-CG. In particular, Swarm-CG has been developed to optimize bonded and non-bonded parameters in molecular models to fit experimental results (top-down references) and the behaviour seen in all-atom MD trajectories (bottom-up references). Swarm-CG has been successfully tested to optimize a variety of molecular systems (e.g., lipid models 26 ). In this paper, Swarm-CG has been adapted for this specific case study (a dedicated variant can be found at: https: //github.com/GMPavanLab/wateropti). The five parameters of a general three-site rigid water model that are iteratively tuned (illustrated in Figure ) are: (i) the intramolecular distance between the Oxygen and the Hydrogen sites, d OH , (ii) the intramolecular distance between the two Hydrogen sites, d HH , (iii) the absolute charge of the Oxygen site, q, and the two functional parameters of the Lennard-Jones potential which is centered on the Oxygen site, namely (iv) sigma σ and (v) epsilon ε. We conducted our optimizations initializing swarms composed of 15 particles in the first and third subsections of the results, and 26 particles in the second subsection. In each optimization procedure, a series of classical molecular dynamics simulations are performed and their discrepancy from the target properties is evaluated according to a scoring function (described below). Finally, the obtained optimized models are simulated at various temperature across the liquid regime, and observables of interest are computed.