Chances are you'll be luckier than I and you'll get a warm day when you visit the ancient paintings at La Trinidad Cave in Mexico's Baja California Sur.
But I was there in the cool of January and gritted my teeth as I dived into the cold river that meanders through a canyon of rock the colors of chocolate and cinnamon.
This is a rite of passage — quite literally — required to see the fascinating prehistoric images at La Trinidad, named for the three-peaked mountain above the canyon.
Guide Salvador Castro Drew's e-mail the day before was terse and slightly mysterious: "Meet at the town arch at 9 tomorrow and bring your swimsuit."
It all became clear after a bumpy, four-wheel-drive journey across the desert and a 20-minute hike during which we examined petroglyphs at trailside.
The river wasn't wide, but it was deep enough to require swimming to reach our destination. Giant boulders were conveniently placed to provide privacy as other tour-goers and I changed into our swim togs.
As we shook like wet dogs and climbed to the cave site, we saw that it was worth it.
Rustic figures
The cave had collapsed some years earlier, but that didn't obscure the rustic figures of animals, fish and humans in daubs of black, white and red that festoon the entry wall.