Observations by cave divers of the nature and contexts of clastic sedimentary deposits in Yorkshire Dales caves, especially those within water-filled phreatic conduits, are gradually being collected and interpreted. Insights into the age, history, relationships and dynamics of the clastic materials are emerging alongside more obvious basic data such as sediment grain size, clast lithology and possible clast provenance. Potentially these and other aspects have wider relevance to other karst issues, including studies of palaeo-hydrology and sequences of conduit development; they can also provide pointers to the whereabouts and possible significance of currently unknown cave passages.