How to Freeze the Fountain with Ice Beam in Pokemon Legends: Z-A

For Main Mission 19 in Pokemon Legends: Z-A, you will eventually need to help Ivor find his little sister, Gywnn, with the help of Detective Emma. The trio will realize that Gwynn might be in the sewers, so you need to use the Ice-type move, Ice Beam, to freeze the Clawitzer fountain and make the water stop.