The objective of this monograph is to synthesise the current knowledge on the nature and distribution of geogenic reefs in UK waters, and to discuss how anthropogenic activities such as aggregate extraction and other marine industries may affect the integrity of these features. There are a large number of geogenic feature types, which have been formed over many thousands of years by glacial, geological and marine processes. Generically however, geogenic reefs may be categorised as either bedrock or stony features. Geogenic reefs support a diverse range of flora and fauna and thus represent important habitats, some of which are protected by environmental designations. Consideration is also given to the morphology and distribution of more general gravel and mixed sand/gravel habitats, which are a primary source of marine aggregate. Marine aggregate dredging has the potential to affect geogenic reefs either directly (in the case of stony reefs) by the removal of sediment, or indirectly through changes to the hydrodynamic or sedimentary regime. However, the consenting of aggregate licences is tightly controlled in order to prevent large changes in physical processes. Therefore, compared with the effects of other anthropogenic activities, aggregate dredging does not represent a major threat to the integrity of geogenic reefs, provided that dredging does not take place either directly on or very close to a feature.