Abstract The exploration of unconsolidated and semi-consolidated strata is generally undertaken using shell and auger and continuous flight augering techniques. These methods have serious limitations, especially when accurate sampling is required below the water table. To improve the reliability of samples British Industrial Sand Ltd. have developed a drill bit for use with reverse circulation drilling. When used in combination with a non-return valve this method allows continuous drilling and sampling both above and below the water table. Comparisons with other drilling techniques show that the duo-pipe method is capable of delivering uncontaminated samples and recovering material of all anticipated size ranges. The system could be adapted for use in the exploration of other mineral deposits e.g. alluvial tin, beach sands, sand and gravel, or for offshore drilling programmes.