Walking. Takes about 20 minutes and you aren't at the mercy of Disney transportation. At the end of your park day, you can have fun taking the Skyliner to Epcot (very close to Beach Club) when you aren't in any hurry.
If you're able to, walk. You'll also be able to be ahead of anyone else who arrives by car or on Disney transportation as long as you leave early enough - we generally leave no later than 7:30 when walking and that's worked pretty well for us (any later and you'll inevitably be behind some of the other transportation).
Walking is the fastest and most dependable. But if walking is not an option, I’d take the boat. It goes directly to DHS, whereas the Skyliner would require a transfer at CBR, and lines there are quite long prior to rope drop.