To return to the boat in Behind the Lock in God of War go around rock to the right of the area and help the boy up the the upper platform:

Help the boy to the upper platform to return to the boat in Behind the Lock in God of War.
Go the the wheel and pull the platform to the other end. Throw the axe at the disk above the platform to freeze it in place:

Throw the axe at the disc to freeze the platform in place to return to the boat in Behind the Lock in God of War.
Instruct the boy to drop the chain and climb up the chain. Get onto the platform and recall the axe.