This paper investigates the reflection of a tsunami due to a quay wall and the behavior of a drifted vessel due to the tsunami by using hydraulic experiments and a numerical model based on MARS with the body force type of IB method. A reflection coefficient is evaluated by considering the difference between water surface elevations in the presence of the wall and those in the absence of the wall. It is found that the height of the wall has a great influence on the reflection, and hence the tsunami run-up. When the vessel is run up over the wall, it is drifted at the velocity faster than the fluid velocity. On an apron behind the wall, it is drifted at the almost same velocity as the fluid velocity. It is also revealed that the vessel can be run up on the apron when the water depth at the wall is larger than the draft of the vessel.