This is precisely why the Bishui Yu managed to evade several major capture attempts.
It wasn't just her who wanted the Bishui Pearl, many prominent figures sought it as well. Unfortunately, this incredibly cunning Bishui Yu has never been caught.
Bishui Yu is a natural spiritual object, with keen senses and a strong awareness. Once it realizes it can't win, it will hide.
It is an amphibious spirit beast, capable of gliding over roofs and walls, and also swimming freely underwater, making it tough to catch within the sprawling water caves.
She didn't plan to brazenly enter the water caves to capture Bishui Yu due to many past failures. These failures taught her that capturing Bishui Yu must be approached with caution.
Therefore, she thought of a clever plan.
She planned to use Lin Yifan as bait to lure Bishui Yu out; but first, they needed to set up a Heavenly Net.
A smart hunter uses traps to capture prey, and she was applying this principle.
