Particle-based simulations are widely used to simulate fluids. We present a real-time rendering method for the results of particle-based simulations of water. Traditional approaches to visualize the results of particlebased simulations construct water surfaces that are usually represented by polygons. To construct the water surfaces from the results of particle-based simulations, a density function is assigned to each particle and a density field is computed by accumulating the values of the density functions of all particles. However, the computation of the density field is time-consuming. To address this problem, we propose an efficient calculation of density field using a graphics processing unit (GPU). We presents a rendering method for water surfaces sampled by points. The use of the GPU permits efficient simulation of optical effects such as refraction, reflection, and caustics. Keywords Real-time rendering