<p>The high efficiency of water jet propulsion and the stability of navigation are two key design indicators of jet boats. In this study, a numerical method is proposed to predict the navigation speed and attitude of a jet-propelled boat by using several key techniques. The six degrees of freedom (6-DOF) method is used to calculate the real-time attitude of the boat based on the momentum balance. To facilitate attitude adjustments, local mesh smoothing and reconstruction techniques are applied. The Volume of Fluid (VOF) method and open channel boundary conditions are used to capture the free surface variations induced by changes in hull posture and jet flow from the nozzle. Under a given jet mass flow condition, the sailing speed of the boat is dynamically adjusted and ultimately determined based on the monitored resistance on the hull. The results demonstrate that this study provides a rapid numerical prediction method for assessing the navigation speed, resistance, and attitude of high-speed vessels. It also provides valuable reference insights for the design and operation of actual water jet-propelled jet boats.</p>