An oscillating grid water tank is used to collect data on the dispersive spreading of a cluster of floating particles in a horizontally homogeneous turbulent field. It is shown that the rate of relative diffusion increases with increasing distance between neighboring particles until the distance exceeds the scale of the energy containing eddies generated in the tank. A diffusion diagram is used to compare the laboratory results with collections of oceanic diffusion data. The results indicate Richardson's 4/3 power law of oceanic relative diffusion can be modeled in the laboratory.