To pop this you must avoid touching the purple water that damages you from the very beginning of the game until you finish the large escape sequence (you'll know it when youre there, about 2.5-3 hours into the game depending on how much you explore). On my speedrun I finished from the game's start through this first escape sequence in under about 45mins.
I previously said I treated the water like a death and deleted my save to restore a backup, but Maka has pointed out below that all you need to do is quit out as soon as you touch the purple water, before you die or jump back out onto solid ground. As long as you don't die or jump out the game doesn't save, so quitting to the menu and resuming is sufficient. No need to restore a backup and loose progress.
In the video below the wellspring escape is at the 46min 40sec mark.