Mulga snake prob the only Aussie snake with any chance of even penetrating a gumboot, most snakes won't even get through denim. Mulga's are *******s mostly because of how vicious their bite is, with the tendency to hold on and chew to deliver the maximum dose of venom, which happens to be the highest dose out of our venomous friends, toxicity being lower than the likes of the Eastern Brown, Taipan, Tiger but made up for with the massive 150mg in one bite, it puts the Mulga at #6 on the list.
I remember moving some drums of fuel years ago and they were sitting in that powdery bulldust dirt, next thing I felt something hitting my boot, looked down to see a Death Adder striking me over and over but it had no chance getting me through leather boots and jeans, lol I still moved pretty fast. Another time I was pig hunting and a Brown or Taipan hit me on the jeans down low, it moved too quick for me to even tell what it was, I thought I was a goner for sure! But it didn't get through the denim thankfully, no snake bite kit on me back then either and at least 45 mins on foot from help.