True or False Test have been conducted to mine uranium from seawater. Just not sure.
Pat==
I checked at www.google.com by typing in "uranium sea water" without the quotation marks and I received a lot of "hits" but almost all that I saw (all but one) were studies to extract U from sea water, studies on the amount of U in sea water, studies on how much U might be needed from sea water, and a lot of hypotheses on extraction techniques. I saw very little from government sources or from review journals. However, I did find one site, which I copied below, in which the author (an individual) reported that Japan had actually conducted a test and formed some "yellow cake". I didn't read the entire article but I didn't see any references. Perhaps some are there. I don't know how reliable the information is but this should give you a starting point.
http://peakoildebunked.blogspot.com/2006/01/207-uranium-from-seawater-part-1.html