I would say that you have to take the monorail. It should be pretty quick, but just make sure you give yourself enough time. The boats probably leave that early, but it may take quite a bit longer. The monorail also lets you off in the Poly building, rather than a boat where you will also have to add walking time to get to the building from the dock.
Nikky, if you're asking about traveling from the GF to the Polynesian (I think you are), then another option is walking to the Polynesian. It's not very far (fairly easy 10 minute walk) and the route is nice. The pathway is along the beach, and at 7:30 or so, I bet the sunrise will be very scenic.
Just seconding the walking suggestion. When staying at the Poly last January we had a couple reservations at the GF and we walked everytime, it wasn't a very long walk, and was much more pleasent than taking the monorail just because our reservations were at peak traveling times.
I agree that the walk between the two Resorts sounds like a nice thing to do and it would be the quickest way to get there. When my family and I stay at the Polynesian this December we are going to walk to the Grand Floridian, so we can say we done it.