When someone's going for a swim swim, it means they're doing it for real, laps and all, and not just frolicking. If they're going to a party, that's probably going to be less party-like than a party party. These are examples of what linguists call contrastive focus reduplication, in which we emphasize a term, or suggest the purest meaning of a term, by reusing it rather than tacking on another adjective. For example, you might just like someone, but then again you maybe you like like them. This is part of a complete episode.
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"Reduplication" seems redundant redundant. If you duplicate it over again, doesn't that result in: "swim swim swim"? I suppose linguists will persist in using the word, irregardless  of my post.