Once a Fountain has been activated, vaccing up some water from it will grant the Ancient Water effect. The Water Tank HUD will become sparkly and flash in rainbow colours, and the Water Tank's stack number is replaced with a timer counting down from 29 seconds. In this time the Vacpack's water supply is unlimited, and the water globs have a subtle rainbow sheen which leave sparkly particles when it comes into contact with a surface or a Slime. When the effect wears off, it will leave the Water Tank with normal Water at maximum capacity.
- For convenience, it may be an idea to have a Teleporter based near a Fountain and using it to instantly replenish your Water Supply when stocks are low.
- The infinite water effect is useful for splashing Harmful Slimes while doing Plort collections, without having to worry about running out of water.
- When Ancient Water is activated, splashes can kill a Tarr in one hit regardless of the time of day.
- Before Ponds were changed to provide unlimited water like other water nodes, Ancient Water could not be used to fill them. Though the regular water left over from the effect could.