Heat Seeking Harpoon

This +1 striking Harpoon has a vicious iron tip that pulls it unerringly toward its target. As long as the target is warm-blooded, has the fire trait, or otherwise has an unusual heat signature, attacks with the heat-seeking harpoon don't take the normal penalties and restrictions for being used in water or underwater. They also ignore any concealment granted by smoke, darkness, or other visual barriers.