Level 19. Water Torture

Start in front of the burned place. Grab any items and dive into the water in the center of your (minimap (the small circular map in the bottom-left corner of your screen) - a small map displayed on your HUD (heads-up display — the on-screen icons showing health, ammo and the minimap)).

Look for a vent in front of a small medikit. Go through the vent to reach the other side.

Go through the opening and dive up. Jump out and kill the ninjas attacking you.

The lift ahead requires the red key, and the door next to it requires the yellow key. Go through the other door and kill the ninjas.

Jump to the "10" Submarine and kill the ninjas.

Jump back up the way you came in, then set your compass to East. Jump there and kill the ninjas.

Locate a red-lit room next to a red cabinet. Dive down and kill the baby rippers. Proceed through the door ahead.

You will find a girl with a mechanic screwer and moving columns. Check the column that isn't moving; it will descend, revealing the BLUE KEYCARD.

Return to the blue key door, located right outside the red-lit room. Use the BLUE KEYCARD on it and go through.

Continue down the blue corridor and enter the first room on your right, the bedroom, to find items.

On top of the bedroom are vents. After you are done, hit the fuel tank, causing the corridor to flood. The doors will lock.

To get oxygen, dive back up to where you started the level. Swim back to the bedroom and face East. Go up to the vent there to find the RED KEYCARD. Another vent nearby contains sticky bombs.

Now, dive back up, being cautious of ninjas waiting.

Make your way to the red key lift using the path described earlier. Use the RED KEYCARD on it and take the lift.

You will arrive in the computer room with Rippers. Kill all Rippers and grab the GREEN KEYCARD. The other door is locked due to water.

Go back to the outside of the BLUE key door. Set your compass to NorthWest and head there. Go through the door and kill all enemies.

Open the next door and kill the Guardian.

Take the first left, keep going South, and turn right. Climb the ladder, turn left, and use your GREEN KEYCARD on the "Authorized Personnel" door.

Kill the Shadow Ninja inside and collect the shotshells and fortune cookie. Hit the switch.

The lift will start moving. Head back out and jump on the lift. It will take you to the previously unreachable area. Jump there and kill the Guardian.

Go through the other door and kill the enemies.

Pick up the YELLOW KEYCARD on the other side. The yellow key door is in front of you, but using it will return you to a familiar area.

Go back to where you rode the moving lift. Use the yellow key on the yellow key door there and go through.

Down the yellow path is a switch; hit it, and the lift will rise. Take the lift down and kill the Coolies and Shadow Ninja.

Enter the room and find a remote control. Through the window is a mini-watertank. Use the remote control to blow a hole through the steel door by targeting the crack in the middle.

Make your way back under the "10" Submarine underwater and swim to the hole you just created. Grab the grenade ammo and swim up.

Kill the two Serpent Gods shooting fireballs at you. Jump up to the path to find and hit the end level switch to finish the level.