Objects interacting with fluid are of high interest to visually present in three-dimensional applications, such as computer games and virtual environments. For presenting the interactions with high correctness, dynamic rigid body simulation may be used. This paper presents methods for efficient, physics-based real-time simulation of fluid-immersed rigid bodies, where the correctness of the simulation is maintained. Simulated forces include gravity, buoyancy, thrust, drag, and lift. To have the simulation run efficiently in real-time, discretization of the simulated rigid body is made by applying mentioned forces to a user-defined number of particles, sampled pseudo-randomly within the rigid body.