The major advantages of a deepwater outfall are the rapid and extensive mixing of the effluent with seawater and the use of natural ocean stratification to obtain a submerged effluent field. A simple design chart for predicting the initial dilution produced by a deepwater outfall (i.e., in a water depth greater than 20 m) in an unstratified ocean is presented. It is demonstrated that, for depwater outfalls, the buoyancy of the discharge has a much larger influence upon initial dilution than the initial momentum of the discharge. Consequently, it is not necessary to provide high exit velocities to achieve large initial dilutions.