Safari Room 3F (2)

From the 2F corridor, go left, down, right, and up the stairs to 3F.

Enter the door on Luigi's right (the left door is a trap).

In this room, locate the Golden Mouse near the big chair. The lamps may hold money, and the chest near the chair always holds a heart.

Be aware that you will face eight Water Elemental Ghosts in total. Remember not to spray ice on them until the water icon inside them disappears, not until they disappear entirely.

Vacuum the boxes (not the crates). Two Water Elemental Ghosts will appear. Spray them with ice, then attack normally.

After this battle, two more Water Elemental Ghosts will appear along with two Bomb Droppers. Defeat the Water Elemental Ghosts first.

A final set of ghosts will appear: four Water Elemental Ghosts and two Pink Ghosts. Try to position yourself in a corner and use your remaining ice on them, ensuring the ice doesn't disappear before you've removed the water icons from all ghosts. Attack any remaining ghosts as usual. If many ghosts are left, stun them if it becomes tough.

After all battles, grab the key that leads to the boss.