You are on the right trail but I was thinking how to transport the water that will not harm the lake. If it works on this sigil, we will try it on the other one near the lake with salt water.

[Double the salt. Mmmm.]

What if we created a path for the blessed water to travel to the sigil? For the ayakashi within, they will not be able to fight as well if they are practically surrounded by what can cause harm to them.