They will walk behind Yahweh - the idea is that the lion cub walks behind its mother in complete safety due to the strength of its mother. The roar is the shout of the archangel at the second advent. The crescendo of the roar is well portrayed by the language here. Trembling from the waters is a portrayal of human childbirth. Ancient writers often described childbirth as coming through or from the waters because of the similarity between amniotic fluid and water.
Trembling is just right for the physical status of a newborn child.
The second advent is the rebirth of Israel. Their new home will be the millennial earth. And this is a declaration of Yahweh. It will certainly come true Verse twelve more properly belongs as the first verse of the twelfth chapter. We will leave it until then.