flood in(to) (something)
1. Of a liquid, to move quickly into something. I turned on the tap at full-blast, and water flooded into the bathtub.
2. By extension, to move quickly into some place or thing in large numbers. As soon as the bell rang, kids began flooding into the school building.
flood in
(to something) 1. Lit. [for a fluid] to flow quickly into something in great volume. The water flooded in and soaked the carpets.
2. Fig. [for large amounts or numbers or people or things] to pour or rush into something. The people flooded into the hall. We opened the door, and the dogs and cats flooded in.