A snakes fags are not armor piercing. Any boot with a good cordura upper that covers your calf will be fine. As far as waterproof, those are a little hard to find where the waterproofing is as advertised. I have a set of Rocky's ( I think they are called Lynx or some such) that are very comfortable and I have yet to have them leak when creek crossing.
Whenever I bowhunt down south or in Texas Snakes are most definitely a concern. I usually carry a .22 pistol loaded with "snake/rat shot" Or a little derringer that takes .410 shotgun. But its the ones you don't see that get you.