This paper provides a compendium of the numerical model that goes under the name of FloodW. This code is a fast tool for the simulation and the analysis of the effects of flooding water on ship dynamics and loads in time domain, developed for safety purposes. It has been recently involved in the international benchmark study on simulation of flooding and motions of damaged Ropax vessels within the EU Horizon 2020 project FLARE, where the name FloodW was given for the first time. Indeed, the development of the code started almost 10 years ago for still water applications, limited to ship motions, up to flooding simulation in regular waves with the possibility to study also non-linear hull girder loads. The core feature of the flooding water modeling is in the assumption of a free surface normal to the apparent gravity vector, which is evaluated accounting for ship and water dynamics. Although this approach, from validations with experimental data, was found accurate in the whole range of filling levels of the damaged compartment, with finer accuracy for intermediate fillings, an alternative method was also proposed and implemented, pertinent to low filling levels. Therefore, this paper provides a comprehensive description of the FloodW code together with its applications, including also the recent developments in participating to the benchmark FLARE, regarding ship flooding in irregular wave scenario.