Actually, if implemented right, it could work. It'd have to be difficult to build, though.
It wouldn't be a laser gun, as OP seems to be suggesting, but rather a shootable spear or harpoon (something I suggested in my own post). It would need a large base, though, like the tree planter, so you'd have to be well-prepared. It would also require a lot of every supply item, and several spears. You could shoot spears at the shark, assuming you have a clear line of sight and good aim. If harpoons (basically just spears with rope tied to them) are implemented, that'd make it easier to reel the shark in to kill it, or, if it goes with my post, have the shark pull you around.