Harpoon gun
From Tomb Raider Wiki
The Harpoon gun has been available as a weapon in Tomb Raider II, Tomb Raider III and Tomb Raider Underworld. It is unique as it can be used underwater and above water. Technically, the weapon is not a harpoon gun, but a spear gun. The spear of a spear gun can be propelled through elastic power, pneumatics, an explosive charge or compressed air, though it is most likely that the spear gun of the games is powered by the last.
