We don't have to do it at all. QPict will do it for us. With all our seascapes selected we simply pull down the customizable Scripts menu and select Add Keyword. Type the keyword into the dialog box that pops up and in the blink of an eye, the selection has the keyword added. You can remove a keyword just as easily.
Categories work the same way.
And, similarly, you can add comments, filenames, and quite a few other notations. Adobe Photoshop and Canto Cumulus both understand ANPA notation, so your QPict work won't be wasted in those programs. Power like that is dangerous, of course. Because it is, by nature, undoable, you can destroy your index or lose critical information in your image if you are careless. But changes can be applied solely to the easily duplicated index file, if you prefer to play it safe.