Nouns ending in -eau are usually masculine.
Is seau masculine or feminine?
leseau
The rule behind it
93.1% of -eau nouns are masculine
In context
J'ai versé l'eau dans le seau.
I poured water into the bucket.
Il y a un trou dans ce seau.
There's a hole in this bucket.
Tom remplit le seau jusqu'à ras bord.
Tom filled the bucket to the top.