Wind Waker Diving allows you to plummet downward by getting pushed off of a ledge after Link plays the Wind Waker for a certain amount of time, around 1.5 seconds. This can be done with any item that has a cutscene, but the Wind Waker is preferred, as the duration of the dive can be controlled. This can be used to "dive" underwater and swim beneath islands. It can also be used to dive into the void without being warped to the start of the room.
Place an object near a ledge, so that Link has just enough space to stand on the ledge beside the object in a sideways fashion, then pull out the Wind Waker. If Link's animation cycle is correct, he will bob away and then into the object which will push him off of the ledge hopefully after a long enough time has passed. If Link automatically comes out of the Wind Waker mode, then he fell too soon.