Also, concerning the Guardian,
I don't think the water monster = guardian. Even though some of the sound files assigned to the water monster are under guardian, I don't think they're the same thing. Some of the audio files for the guardian, which are not used in game, are massive ground shaking, terrifying roars. I think that the guardian was supposed to be a massive monster but never made it a functional enemy in the game, except for the shadow manifestation in the youtube video I just posted.