Hey Pearl,
Pretty sure he ditched the spear gun in favour of an "iki spike". It's a small pointed stainless shaft designed to kill a fish by spiking it in the brain to stop its fighting (iki jimi).
It would be useless to kill the shark but a quick prod into it's sensitive snout is a good deterent, unless the shark really wanted him for lunch in which case he would be f&%ked!
Good winds,