Vidi Aquam
Vidi Aquam is one of the two antiphons sung during the Rite of Sprinkling with Holy Water, at the beginning of a Sunday mass.
Vidi Aquam is the antiphon used during Eastertide, while Asperges Me is used outside of Eastertide.
From Easter Sunday until Pentecost:
Ant. I beheld water issuing out from the right side of the temple: alleluia. It brought God's life and his salvation, and the people sang in joyful praise: alleluia, alleluia.
(Ps 118) O give thanks unto the Lord, for he is gracious; because his mercy endureth forever.
(Bow) Glory be to the father, and to the Son, and to the Holy Ghost: (Rise) As it was in the beginning, is now and ever shall be, world without end. Amen.
Ant. I beheld water issuing out from the right side of the temple: alleluia. It brought God's life and his salvation, and the people sang in joyful praise: alleluia, alleluia.
DWM pg. 1044