Question About Diagramming

This has to do with indirect objects. Take these two sentences for example:

1. The ship's captain gave the crew orders.
2. The ship's captain gave orders to the crew.

The first sentence is easy to diagram: subject=captain, verb=gave, indirect object=crew, direct object=orders.

However, I am having trouble with the second one, mainly the prepositional phrase "to the crew". It seems to function as an indirect object by telling for whom the action was done, but prepositional phrases cannot be indirect objects. So is the prepositional phrase "to the crew" functioning as an adverb or an adjective? It does not seem to function as an adverb because it does not sufficiently answer any of the adverb questions (Where?, When?, How?, How often?, How long?, To what extent?, How much?, or Why?). So is it functioning as an adjective describing "orders"? Any help would be appreciated.

Solution 1:

In a comment, John Lawler wrote:

There's no difference between the two sentences; they are simply the two variants of the Dative Alternation. If you believe that only one of them can contain a real Indirect Object, then you need a definition of Indirect Object that tells which one and why. Myself, I'd say the crew was the indirect object in either case, whether it had a preposition or not. Rather like This bed was slept in by George Washington, where the passive subject is derived from a prepositional phrase, not a direct object, but it's close enough for Passive.