The fisherman finishes his story and gets one promise out of the jinni. That he will not be harmed. Then he opens the bottle.
This time the jinni keeps his word. He takes the fisherman over the mountain. There is a lake there, ringed by mountains.
The fisherman has never seen that water before. He has lived by the sea all his life and knew nothing of this lake. Mountains close it in on every side, so from outside there is nothing to see.