Help me with waterhole

[warm obsidian]

How to complete the duel feats challenge of turning into a waterhole while it waits to use its sneak attack?

[shrewd pilot]

Use flipendo on a resting Dugbog

[warm obsidian]

I'll try... the problem is that I don't know when exactly he's resting, whenever I get close when he's invisible it seems like he's already on alert