It all comes back to water, right?
Bodies of water, especially deep ones, are usually associated with darkness. There's the sunlit zone, the twilight zone, the midnight zone, the abyss, and then the trenches. It gets darker yet darker the deeper and deeper you go and colors start to shift.
Dark Fountains that are the power sources that give birth to Dark Worlds.
The term for when darkness takes over the light is "roaring" which is. a very common sound description for waves and rushing water.
SO MANY mentions of waves. Notably the section of Raise Up Your Bat where it says "Which shall guide you the way, through the waves"
The lake in town that has Onion, Clam Guy, the Striped Bird, and the song from far away. (Clam Guy and the Striped Bird who have Goner variants...which could mean nothing)
The underwater background we see when creating the vessel...IMAGE_DEPTHS
Going back to Raise Up Your Bat once more... to the beginning of the section.
"Come follow me into the dark
With your heart as the ark
Which shall shine you the way"
On the assumption that the roaring will happen in chapter 6 or 7. The apocalyptic event would be a flood as darkness washes over the land. Throughout history there have been many flood or deluge myths, most of which involve a culture hero (whether Noah, Manu, Shuruppak, etc.) who built a boat, or an Ark, in order to survive the coming flood.
And then there's the Weird Route (or Snowgrave or B Side)...
For there to even be fountains there needs to be a source. While I think the Lake could be a dark world, I am far more partial to the idea that during the weird route our favorite glitch hunter Noelle found the glitch once more. She literally takes advantage of the player ability to make decisions above everything else in the game (as the player did during the Chapter 4 in her house) to force a proceed by giving us action cues.
Like finding a key item in a video game Noelle used us to help boundary break...
And then there’s the bread and punch card references. Sans refers to the card as a Punch Card which is arguably Undertales most famous glitch that lets you sequence break and go out of bounds. And Sans also gives us the Bread, which is part of a very famous Mother glitch (Bread Crumbs) that also allows for boundary breaking. (Which is probably why Bread is the forbidden technique to Malius)
And then there's her blog. Noelle has been associated with glitches since the Spamton Sweepstakes whether in Cat Petterz or Dragon Blazers.
"…remembered to hold my breath halfway XD Now I was going to be able to see what was in the secret door…"
And as we know from our require reading (Undertale) what is necessary to break barriers?
