The bronze harpoon is a tool used for harpooning fish in the fishing skill and is capable of catching 5% more fish than a regular harpoon. The harpoon can be smithed using the smithing skill at level 3 Smithing, using 1 bronze bar. The harpoon may also be gained as a drop from Celestial water warriors as a common drop, but there's a very high leveled requirement to fight these creatures.