A vast resource of gem-quality diamonds exists off the west coast of southern Africa. Over the course of millions of years, many diamond-bearing kimberlite pipes in the Orange River drainage basin have been extensively eroded and the released diamonds transported to the west coast. Raised marine deposits now on land have yielded almost 100 million carats of predominantly gem diamonds; similar marine deposits and feeder channels are now known to exist offshore. Techniques for exploiting the offshore resources have been proved on a small scale in shallow (<I5 m) waters. New technological developments in underwater mining systems have progressed to the point where mining has commenced in deep (about 100 m) Namibian waters. It is anticipated that production of diamonds from the sea will increase substantially in the future.