Water Bucket
minecraft:water_bucket
Obtained in loot chests (Village (village fisher)). Doesn't stack.
How to get it
No direct recipe — it's made using a Bucket:
Crafting 
→ 
Bucket
📦 Found in chests
Village (village fisher)
Villagers buy this
Wandering Trader · Novice 1 → 
2 Emerald
1 2 Emerald