Abstract: A device for preventing water pollution is provided, to collect and retain liquid fuel overflow from fuel tanks for boats and similar vessels. The device is designed to collect fuel discharged from the air vent of an enclosed fuel storage tank, when the tank is refilled. A support ring is affixed to the external surface of the hull of the boat, telescopically relative to the air vent protruding threfrom. A hollow receptacle is adapted to be mounted on the support ring, for collecting fuel discharged from the vent. A retainer sustains the receptacle on the support, and locking means detachably secures the retainer to the support, while the receptacle is collecting fuel discharged or spilled from the air vent.