I spent many, many days tromping around in near-freezing rivers while whitewater rafting. Thick wool or fleece socks don’t work. Cold water flows in, and warms up for a while, and you think all is right with the world. The next time you step in the river, more cold water flows in, and warmth/happiness drops dramatically. And you are constantly “squish-squish-squishing” as you walk, which reminds you of how cold your feet are or will soon become.
All the cold-water rafters and kayakers I knew wore drysuits with booties (not practical for backpacking), neoprene boots (also not practical), or neoprene socks inside extra large shoes or sandals.
I went on several multi-mile side hikes in neoprene socks inside tennis shoes or river sandals (early Tevas or Chacos). Even in warm sunny weather, neoprene socks act like a kind of vapor barrier, so your feet don’t sweat that much. Gets kind of funky inside, recommend rinsing or washing daily. Tried liner socks – didn’t like them at all.
But it sucked to put on cold, wet, sometimes frozen neoprene socks in the morning. They warm up quickly if you’re moving around, though.
Super-thin neoprene socks basically have no insulation value. You need a couple of millimeters or more to retain real warmth. 2-3 mm should be fine; anything more would be too warm.
Perforated neoprene wasn’t available when I was rafting, don’t know anything about that.
— Rex