Instructions
Run to the middle of the submarine immediately after you plant the second explosive and kill any enemies along the way. Face the ladder you used to enter the submarine and look up. Move toward the ladder to climb it and exit to the submarine's exterior.
Crouch when you get off the ladder and look to the right side of the dock. Stand up and kill the guard ahead of you, then crouch again.
Move to the back of the submarine's tower and look down. Kill the two dock workers here. Turn around and return to the front of the submarine tower.
Equip the Springfield rifle and stand up. Press the right mouse button to look through the scope and then shoot the three guards at the far end of the dock.
Jump down from the submarine's tower and run to the ramp that leads onto the dock. Run up this ramp and you will be clear of the explosion.