Hydro Torpedoes Edit
The Hydro Torpedo is a 1993 Nerf ammunition usable in arrow-compatible blasters. It is essentially a blue arrow with red fins and a water-absorbing sponge tip that would leave a wet spot when someone gets hit by it.
Originally, it was going to be the primary ammunition of the Harpoon Crossbow, but the blaster was never released. Instead, the torpedoes were released and distributed as a refill pack.