every metric ton of seawater there is about 10-²
milligrams of gold and there is a heck of a lot of seawater in
the oceans, so if you could come up with an extraction process, you'd
be rich beyond the dreams of avarice. Yup, just anchor your
floating electrolysis factory off the coast and you'll be hauling out
fifty-foot high plates of solid 24-karat goodness by the hundreds
before you can say "Midas."
Mind you, since you'd need to go through a cubic
kilometre of seawater to extract only six kilogram's of gold (worth
about $100,000) it costs far more to pump the water than the gold
could ever be worth, so if you want to make any money on the deal I'd
suggest keeping two sets of books and a first-class ticket on a fast
plane to South America for when the investors find out.