Surah Al-Kahf, Verse 41

أَوۡ يُصۡبِحَ مَآؤُهَا غَوۡرٗا فَلَن تَسۡتَطِيعَ لَهُۥ طَلَبٗا٤١

aw yuṣ'biḥa māuhā ghawran falan tastaṭīʿa lahu ṭalaban

Or its water will become sunken [into the earth], so you would never be able to seek it."