This topic came up before.
Yes. They come down and have a little coverage over the top of the foot but most of them are just calf, shin, and ankle protection. Hopefully you have some nicer quality boots made out of leather or some actual snake boots! The cheap hiking boots from Big 5 probably aren't your best option versus a snake bite.
I have some White Water Gaiters. They weren't expensive and I'll tell you that they are HOT!!! They don't breathe and if you're doing a lot of moving around, prepare for soaking wet legs! Rather have sweaty legs than a snake bite though! I hunt as cheap as possible so they do the same job as the expensive ones (in theory), just have to deal with the discomfort of sweaty legs.
Why not just get a pair of snakeboots .can i get some pros & cons boots vs. gaiters
http://www.cabelas.com/product/Whitewater-Mens-Snakeproof-Gaiters/725400.uts?WT.tsrc=CRR&WT.mc_id=crrdtfd