When you think of gold and diamond mining I bet you think of dark long tunnels or strip mining. Would it surprise you that marine mining, mining for minerals in the ocean is being done by large corporations? Yes marine mining is being done and those companies are looking for diamonds and gold. The main areas of exploration are off the coast of west Africa. The De Beers company, known the world over for their TV commercials for loose diamonds with the phrase "a diamond is forever", is a major marine mining company.
Marine mining is not simple and most smaller companies and hobbyists are just salvaging old ship wrecks and call it mining. The true marine mining vessels are huge ships. like this one:
This is the De Beers diamond recovery vessel PEACE IN AFRICA (former Dock Express 20)