ToME WikiThe entrance to the Small Water Cave can be found on level 40 of Moria. It looks like a purple > in the ASCII mode.
Like its name tells, the Small Water Cave is small, only three levels deep. It is inherently acidic. It will damage you and your equipment unless you have acid immunity. It will or may damage your armor and inventory unless they are artifacts or are otherwise inherently acid-resistant. The terrain is very watery, but water-breathing is not needed. Levitation or flight will prevent you from drowning in deep water tiles.
The Small Water Cave is guarded by the Watcher in the Water. It will drop an artifact and potentially even the One Ring. The corpse of the Watcher in the Water is coveted by some characters who would like to be a Possessor