How can I rescue Halisa

Hint 1 of 11:

Talk to the queen, Halawa, for instructions.

Hint 2 of 11:

Follow along the west bank of the Barako river to the cliffs.

Hint 3 of 11:

(You may see Silverback along the way, up on the cliff.)

Hint 4 of 11:

It is safest to kill Silverback from a distance.

Hint 5 of 11:

You must now tell Halisa that it's OK to leave, but where is she?

Hint 6 of 11:

Did you notice a cave entrance upstream behind the falls?

Hint 7 of 11:

The water effectively stops you from entering the cave.

Hint 8 of 11:

Notice that big boulder up above the falls?

Hint 9 of 11:

A well placed grenade will push the boulder to block the falls.

Hint 10 of 11:

Enter the cave, and follow the tunnel, to get to the upper plateau.