Complete the game.
Collect 50% of the medals.
Neutralize 10 Malthusians in underwater combat.
Kill 2 Malthusians within a timed chain attack.
Kill 5 Mathusians with fire or electricity.
Drown a Malthusian.
Save Chief Billingham.
Complete a hack.
Collect all documents and objects.
Collect all the medals.
Complete the Challenge Room.
Sweep 3 Malthusians off their feet with water.