Freshwater mussel beds of the lower 68 km of the Cache River, Arkansas, were delineated, sampled using dive techniques and a stratified random sampling methodology and analyzed for density and species richness. A total of 38 mussel beds were delineated, 14 major beds (Mbeds) and 24 minor beds (mbeds), and defined by areal extent and mussel density. Analysis of our sampling precision indicated 80% or better confidence levels for a majority of our sites and suggested that a sample size of 15 1-m² quadrats is sufficient to obtain 80% or better confidence. Our large river diver-assisted sampling methodology has been shown to be a useful and appropriate methodology for obtaining large geographic scale baseline distribution (bed and species), species richness, density and population and community numerical standing crop estimates information where tradeoffs are required in order to complete a project within time and budget constraints.