Ocean waters do hold gold – nearly 20 million tons of it. However, if you were hoping make your fortune mining the sea, consider this: Gold in the ocean is so dilute that its concentration is on the order of parts per trillion. Each liter of seawater contains, on average, about 13 billionths of a gram of gold.
There is also (undissolved) gold in/on the seafloor. The ocean, however, is deep, meaning that gold deposits are a mile or two under water. And once you reach the ocean floor, you’ll find that gold deposits are also encased in rock that must be mined through. Not easy.
Currently, there really isn’t a cost-effective way to mine or extract gold from the ocean to make a profit. But, if we could extract all of that gold, there’s enough of it that each person on Earth could have nine pounds of the precious metal. Eureka!