Socks for trail running shoes that get wet?

40 river crossings?!! Where the heck were you -- Big Frog / Cohutta?

I'm not a big proponent of trail runners for backpacking, preferring waterproof boots for that reason. But here's a little trick I learned when my kids were little. Stick bread bags (think wonder bread) over their dry socks before slipping them in their boots.

Kids hiking shoes are rarely waterproof, and you don't want to spend a lot of money on them as they outgrow them on a yearly basis.

I carry a pair of sandals for river crossings.

Maybe I'm lucky, but I've had no problem hiking all day in soaking wet wool socks (as long as my boots fit well).

Well, "comfortable" is the word I would choose, but once I was wore Smartwool socks when I crossed the Payette River with boots on, and they were wet for a day and a half, about 14 miles altogether.   I've hiked pretty far in wet REI socks, which have a higher wool content than Smartwool, according to the label.  Neither was as abrasive as wet cotton socks, but I was careful to avoid letting them bunch up anywhere.  I also took my boots up a few times during the day to let my skin dry out.

That was one of the few times I ever intentionally wore boots in the water.  It was wide, deep and rocky, and I couldn't see the bottom.   Altogether I crossed three times.  I've also hiked long distances in boots/socks thoroughly soaked by rain.  Among the worst was last fall in AZ, when the temps plummeted after an all-day rainstorm to finish with three inches of snow.  My boots were frozen solid in the morning and my socks were still wet.   Getting my boots on was the hardest part of the day.  Ironically, temps were in the 70s by late afternoon.

I swear by WrightSocks. They come in varying thicknesses, and since they are constructed of two separate plys, I don't have issues with blisters even if they're wet/moist. I must have walked/run over 1,000 miles in wet WrightSocks with no blisters.

If it gets too cold to walk with wet socks / trail runners for a considerable length of time (about 1.5 hours @ 30F for me), I switch to boots.

I've used both Wrightsock and Smartwool. Love the Smartwools, which at least in my experience are thinner, which I like - my pups like to breathe. I've only tried one style of Wrightsock, which was a dual layer version, which should be better at preventing blisters. I got blisters anyway, but after 14 miles and 4,000 elevation change, that's not super surprising, especially given the fact that socks aren't the only issue. Either @tdale or cgaphiker swears by Wrightsock. I don't have anything against them, I just normally like thinner socks than the dual layer Wrightsocks I happened to buy. YMMV. HYOH.

I've been wearing trail runners for about 10 years. I like the Montrails that have a full length rock plate, both stiffer and more foot protection.

As to wet trail conditions: no Gore-Tex.  I want the shoe to drain even if it stays wet all day. Wear two pair of socks. For me these are injinji toe socks. against my foot one of the lightweight coolmax. and in warm conditions >60 degrees a second coolmax socks. For cooler conditions one of the injinji lightweight wool socks as the 2nd sock.

Never any problem with the wetness, no blisters, etc. Even 10+ hour >20mile hiking days. At night I wring out the wet socks and hang to dry as much as they will and either go barefoot or put on a dry sock overnight.  If I need to put my shoes on in camp I slip my foot first into a plastic bag to keep them dry inside the wet shoes.  

This works for me as long as morning temps are above freezing.  As to below freezing????just haven't hiked in wet below freezing conditions so don't know the lower limit.