Yasser Lopez, 16, was fishing with a friend when the weapon went off as the pair were loading equipment onto their boat.
The spear entered just above his right eye and penetrated through his brain to the back of his skull.
The medical team revealed that Lopez had been awake and interacting with the emergency team when he arrived at the hospital, which indicated to the doctors that he could survive the ordeal as they planned the surgery.
Miraculously, no vital brain structures were damaged by the harpoon.
Following surgery he could communicate in short sentences with hospital staff but he had no recollection of the accident.