Driftwood goes thru 2 transformations. The initial one happens after you complete the first sidequest. This one allowed you to hit the melee switch when it was out on that rock in the water.
The 2nd transformation will happen to driftwood after you deliver the letter to the carpenter in Mourningwood. Although, I specifically remember that the change doesnt happen immediately. You have to wait a little bit for the carpenter to finish remodeling Driftwood for the 2nd time. After the remodel, there should be a wooden plank walkway that will let you walk up to where the next melee switch is hovering, just at the stump of the tree.