Twitch describes the lightest option, but those don't offer much support for hiking and wading gravel-cobble rivers. The Patagonias are among the lightest (and most comfortable), but my experience with 3 or 4 pair is that they don't last near long enough to amortize their cost. The Simms Freestones are a bit lighter than the Headwaters, I've been wearing those a bit over the last year.

Sg