Lava Waders

Lava Waders allow you to walk on water and lava, give immunity to fire blocks, and give you seven seconds of lava immunity.

The lava immunity effect stacks with Lava Charm for a total of 14 seconds.

Simply standing on the lava does not begin the "burning countdown", making it completely safe to do so. This only happens when you dive in.

Tips
These are very beneficial when killing the Wall of Flesh if you do not have Water Walking Potions or when mining Hellstone.