Both examples use the verb sail + the preposition through. However, because the first sentence uses the literal meaning of sail, we know it is a pr...

Both examples use the verb sail + the preposition through. However, because the first sentence uses the literal meaning of sail, we know it is a prepositional verb—the preposition is merely describing the movement of the verb, without changing the meaning of the verb itself. If, for instance, we change the sentence to "They sailed along the coast," the meaning of sail does not change.