Park to park buses run from:
DAK to Epcot and Studios, To MK you need to go to the TTC and then either ferry or monorail to MK.
Studios to Epcot and DAK, To MK you need to go to the TTC and then either ferry or monorail to MK.
Epcot to DAK and Studios, To MK you need to monorail to TTC and then either transfer to the MK monorail or ferry.
Water Parks require you boarding a DTD bus for Typhoon Lagoon or a DAK bus for Blizzard Beach.