Nouns ending in -eau are usually masculine.
Is vaisseau masculine or feminine?
levaisseau
The rule behind it
93.1% of -eau nouns are masculine
In context
La vaisseau spatial a effectué un atterrissage parfait.
The spaceship made a perfect landing.
Un vaisseau sanguin a éclaté dans mon œil.
A blood vessel broke in my eye.
Je me demande qui a nommé ce vaisseau.
I wonder who named this ship.