Recently, i read an article tat described a process for extracting uranium from seawater. The japanese developers of this feel the process is efficient enough, that the uranium obtained could be a major source of fuel, for fission reactors.
Could the same process be used to extract gold from the sea? What salt/compounds of gold are present in seawater, and how many ounces per cubic mile of ocean water is there?

I believe you meant for this to go to GQ. I’ll move it there for you.

If my googling is reliable, the mass fraction of gold in seawater is around 7 * 10[sup]-13[/sup]. A cubic mile of seawater has a mass of around 4.28 * 10[sup]12[/sup] gm, so full extraction of all its gold would yield around 3 grams, or 0.0963 troy ounces.

At current prices, that’s worth around $63 - probably not enough to offset the cost of pumping several billion tons of water through your factory.

Quite a few people seem to have fantasied about the riches in seawater over the years, but the basic meme dates back to the efforts of Fritz Haber to extract gold from it in the 1920s. Despite Haber being the most important German chemist of the period, this turned out to be a complete wild-goose-chase.
Haber’s initial optimism was based on an earlier estimate of the amount of gold in seawater by Arrhenius. Using this estimate, in 1920 he speculated about extraction as a way for Germany to escape from her war reparations by paying them off in gold (or, if necessary, by dumping large quantities of it on the market and undermining the global economy). He therefore organised several expeditions through the Twenties to verify Arrhenius’s numbers and investigate the possibilities. The initial results were promising, but it gradually became apparent that these were misleading. Eventually he had to conclude that the high values were a result of the samples becoming contaminated by the trace amount of gold in any chemistry lab. In retrospect, the early numbers were orders of magnitude too high.

While Haber abandoned the idea, his interest seems to have been enough to establish the notion in the wider public mind.

Back in the 1970’s, there was a flurry of interest in a system that used a polymeric filter in an ion exchange process. See Seawater Gold Ion Exchange Patent

I think the idea was that you would create a large ion exchanger & drag it through the ocean. They claimed to get anywhere from 2.35 to 6.4 troy ounces of gold over a period of time ranging from 11.7 to 13.5 days. The patent isn’t written very clearly, and it is not clear what the actual flow rate of the sea water through the ion exchanger is.

I haven’t heard anything on this recently - I think it was too impractical to really work on any reasonably large scale

Magnesium was frequently extracted from seawater, through an electrolytic process.

Looking around for similar figures, I found this:

How much would that pound of uranium be worth on the market? Would it be worth the $250 to extract it?

Not today. Yellowcake prices fluctuate but have ranged between about 25-45 dollars per lb this year. Yellowcake consists of mixed uranium oxides and salts rather than the pure metal, but at that price it’s still cheaper to dig uranium ores than to process seawater.