If memory serves, it does. And i definitely remember fighting an ancient rathound - maybe even couple, not sure - there in one of playthroughs.
Thing is, it's probably random, if it is this one from the wiki: "Siphoner Pools (Black Sea) > Underwater rock bridge > 7 Perception > leads to a lingula plant and a
random treasure "crevice""
P.S. Amannamedsquid, if this is the one, then your derangeness is optional. Sort of. Or, intermittent? Random? Episodic? Words are hard... Ah, no, this is the term:
occasional. Now that's one rare state of mind, right?