A heat-proof vessel is a water container given to the player by Petrified Pete upon entering the Volcanic Mine. It can be equipped in the weapon slot. It has 35 uses per game, and can be used to throw water onto the lava, creating platforms which players can walk on. These platforms will melt after 90 seconds, giving players limited time to stand on them. If players remain on the hardened lava when it melts, they will fall into the lava, taking massive damage.
The water can only be thrown while the player is facing north, east, south, and west. Additionally, the water canteen can be right-clicked to open a dialogue box to throw water in a specified direction, or right-clicked while it is equipped to select the direction the player wants to throw it at.
Players can pay Petrified Pete 10,000 Volcanic Mine points to have him upgrade their vessel to hold more water, increasing the number of uses per game from 35 to 70.