The Lagoon - the mercenaries' PT boat - is chased into a river by the military forces, which are chasing primarily in an attack helicopter. It seems the lightly-armed Lagoon has no chance against the helicopter, but Rokuro formulates a plan involving the boat's torpedoes and a partially-sunken ship lodged in the river canal. After defeating the helicopter, the Black Lagoon brings Rokuro to the realization that he has been written off by his former employer. He elects to stay with the mercenaries, who start to call him by the nickname 'Rock'.