It is, indeed, the bus. Typhoon Lagoon shares all of its buses with Downtown Disney, but until about 11 AM (I think that's the switchover time), buses from the resorts will stop at Typhoon Lagoon before continuing on to the Marketplace. After 11, when the Pleasure Island stop opens, the buses will travel from the resorts to Marketplace, PI, and then TL. Blizzard Beach shares its buses with either Animal Kingdom or Epcot or, in the case of the All-Stars, has its own bus. At the Grand Floridian, Blizzard Beach is served by the Animal Kingdom bus.