The last poster is both right and wrong.
There is no park to water park bus for Typhoon Lagoon. You need to get to a resort and use the DTD/TL bus.
There IS park to water park buses for Blizzard Beach. Studios does the AK/BB run, Epcot does the Epcot/CSR/BB run, AK Every resort bus except AKL and AllStars do a park/BB/resort/BB/park run.