In order to develop the supercritical water cooled reactor (SCWR) concept, thermohydraulics of supercritical pressure water is one of the most important areas to be clarified. This publication summarizes the outcome of an IAEA coordinated research project (CRP) on this topic. It provides researchers and engineers with a comprehensive and reliable thermohydraulics database and the current status of prediction methods for SCWR concept development. The publication includes descriptions of SCWR concepts, heat transfer and pressure loss characteristics of supercritical pressure fluids, development of new heat transfer prediction methods, critical flow during depressurization from supercritical conditions, and flow stability and natural circulation in supercritical pressure systems. It also covers the results of two code testing benchmark exercises for steady state heat transfer and flow stability in a heated channel.