Not all resorts have waterway access to a park. However, for those resorts that have water transportation, the docks are well marked. The only one that might be a little difficult is WL, but that's just because its a good distance from the hotel to the dock. There are signs and they're easy to follow.
These are the resorts that i can think of with water transportation to at least one park:
GF, Poly, CR, WL, and FW have water transportation to MK.BW, BC, YC, S, and D have water transportation to Epcot and DHS.