The Pulse Wave Torpedo is a powerful X-Com weapon reverse-engineered from the alien Disruptor Pulse Bomb. For all intents and purposes, it is the aquatic equivalent of the Fusion Ball, but instead of dealing damage with micro-implosions, the superdense PWT warhead simply punches through an Alien Sub's hull at unimaginable speed.
Like the Fusion Ball, the PWT has very high damage, range and 100% accuracy at the cost of being expensive to manufacture and low ammo capacity. The torpedo can sink and even destroy most subs in one to three salvos, and can easily handle subs ranging from medium to large size (and on an unrelated note, it makes a cool noise like electricity crackling when fired). Despite its advantages, most seasoned players do not use PWTs for their subs' weapons, and prefer to use Sonic Oscillators instead. Rather than using them on subs, the PWT sees better use as the armament for the Displacer/PWT (the aquatic equivalent of the hovertank) and in the PWT Defense facility.