The Wet Bone is inside one of the drains inside the pool of the Pool area of the School. It is the second drain from the left, and next to a collectible Item called a Torn Swimsuit. In order to get inside the pool, you must first use the pool's device to drain the pool. Then, you can go inside to get the bone.
- Though to the closeness between this Item and the Torn Swimsuit, this bone may have been a human bone of someone who owned the swimsuit and died there.