The key to enhancing perception of the virtual world is improving mechanisms for interacting with that world. Through providing a sense of touch, haptic rendering is one such mechanism. Many methods efficiently display force between rigid objects, but to achieve a truly realistic virtual environment, haptic interaction with fluids is also essential. In the field of computational fluid dynamics, researchers have developed methods to numerically estimate the resistance due to fluids by solving complex partial differential equations, called the Navier-Stokes equations. However, their estimation techniques, although numerically accurate, are prohibitively time-consuming.This becomes a serious problem for haptic rendering, which requires a high frame rate. To address this issue, the authors developed a method for rapidly estimating and displaying forces acting on a rigid virtual object due to water. They provide an overview of their method together with its implementation and two applications: a lure-fishing simulator and a virtual canoe simulator.