Triggering the Kaernk in the Cistern?

[Cursed Lemon]

I just have a general question.

I remember on my first playthrough, when I entered the Cistern and opened all three valves, the shadow appeared and the Kaernk was actively pursuing me through the water.

I've noticed on my last two playthroughs, however, that the shadow fails to appear and the Kaernk isn't around, even though I heard all of his little splashes and growls and whatnot.

Is there something you have to do to trigger this event?