Resident Evil 2

When the water is drained you can climb down some ledges in that room to get to some boxes, push them towards the wall and press the button, the boxes float up and you can walk across them.

When you enter the room the water should already be drained. The 3 boxes at the bottom of the tank are scattered about. Heres what I like to do: Hop over the first box that is closest to the side with the switch. Then face the box that is in the middle and push it -slightly- to the right. Hop back over that box and it should be already in place in the middle (you might have to mess with it a bit to get it perfect) Then the other 2 boxes that get pushed into place on the end just need a push to the wall. When all 3 boxes are fit into place along the top side of the wall, go back up to the switch by the door and fill the room with water. The boxes will then float up, allowing you to cross over and get the key.

Do the box puzzle then head back to leon she will through the items to him.

Don't forget to go down the red elevator and collect the shotgun shells too.