Offshore mining of placer diamond deposits along the coast of South Africa and Namibia has become a multiscale activity. It is a successful offshoot of a land-based mining industry that has operated along the coastline for more than 80 years. Onshore diamond deposits have been worked by several methods from the foreshore to some kilometers inland (Hodgen). These deposits are the foundation of an ongoing industry along the coastline. The offshore diamond industry began in the late 1950s and has now come of age. Diamonds are produced along 800 km (500 miles) of coastline in water 200 m (660 ft) deep. About half of the coastline is in Namibia, north of the Orange River that defines the border with South Africa. The other half is in South Africa. Coastal diamonds are thought to have been eroded from the upper parts of diamond-bearing pipes in the southern African hinterland (Gurney, Levinson and Smith, 1991). The Orange River carries the released stones west along the river's present and ancestral routes to the south Atlantic. The stones entered the sea at several points between Cape Town and the present Orange River mouth over 400 km (250 miles) during a 60-million-year period.
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