Since the rivers ultimately drain all things from the lands of earth, the seas are full of all kinds of materials. Including fantastic quantities of metals. The only problem is: a single liter of sea water doesn't contain much of a specific metal like gold or uranium, though a cubic mile does.
Story summary (spoiler).
This is the story of a machine that can extract any specified metal from the waters of the seas without consuming awful amounts of energy & in large quantities. The machine is fitted at the bottom of ordinary sea going vessels. So one run across Atlantic can collect a lot of metal for owners of sea liners, e.g. Or a mining company could set the ships moving through the seas, & they can return to the docks when full.
And you save the environment: much lower energy costs in mining metals, & you don't spoil precious land. And there is enough in the seas to meet demand for as long as we can foresee.
End of the story is rather unnatural, but it is generally a readable story. Key part of the story is somewhat descriptive, & happens on board a boat off the Florida coast.
The Man Who Ploughed the Sea, short story, review
Author: Arthur C Clarke
Genre: Science fiction
- "Imperial Earth": A sub-plot in this novel involves genetically engineered marine life to mine gold from sea water.