Chum drops from Skittering Eels in the Abyssal Pool in Nazjatar. The first one is provided as an objective for the quest. Applying the chum to the Eel Infested Waters will summon more of the same eels until finally the Shimmerscale Eel appears.
As a quest objective
- Patch 8.2.0 (2019-06-25): Added.