Your wish has been granted! However, the skill itself is just a buff to let you gather a new type of node. To unlock it you need to attune to the land of Eorzea by gathering Fishing, Mining and Botanist atmas and trading them in for the secret arte of floating - known only to Jalzahn... and anyone else whom he told.

I wish that I could summon Leviathan and ride around on him, and drink deep of the sea's salty broth with him.