After crashing down, grab your pistol and take out the two enemies in front of you. Before drowning, exit the helicopter and follow Reznov to the boat in the distance. Quickly come out of the water and take the guard hostage. Use your human shield to protect yourself and shoot the other enemies with your gun.
Follow Woods and shoot down the enemies on the hills above and through the rivers. After getting a call from Bowman, enter the water again and swim under the next boat. Emerge and quickly stab the guards before they realize what's going on. Sneaking with just your knife and soon Bowman will appear.
Head back underwater and plant the first of two bombs. Next, move back to the surface and find three sleeping soldiers. Cover their mouths and brutally stab them while their cries for help are muffled under your bloody fingers.
Go back underwater and plant a second charge. Keep following your unit and when Woods gives the order, blow up the charges. This will alert the enemy, so be quick about killing them all.
Grab the guns in the building on the left and you'll have plenty of fire power to destroy the enemy. A Boat with a heavy machine gun will emerge far off to the right. Follow Bowman and grab the rocket launcher. It only has a few shots left in it, but one will be enough to take down the boat.
More support will arrive and will help you take down the enemy. If you still have rockets left in the tank, use them to destroy the enemy machine gun nests. Even if you don't manage to take it out yourself, your allies will eventually sort out the problem.
Follow Swift into the tunnels below and he will soon be murdered. Take out the guards ahead and follow Reznov deeper through the cave.
Your hand gun is very strong, able to blow off enemy limbs in only a single shot. Kill every enemy along the way and you'll soon come to the hidden Russian base. After a brief scene, climb out of the cave and use the on screen commands to dig to the outside.