You're most likely to just find water snakes around farm ponds. Cottonmouths prefer slow moving streams. As for tin, etc, copperheads, and lotsa non-venomous, but why not just leave them in the wild, and take pictures. You want to be very careful, and NOT get bit!

As for the ponds drying out, with this intense heat, the snakes are probably mostly underground anyway so you may not find a thing..