Coolsville Harbor is a harbor that is located on Coolsville by the Coolsville Beach. It appears on A Pup Named Scooby-Doo season 2 episode: "Dog Gone Scooby", and in Scooby-Doo (DC Comics) & Scooby-Doo, Where Are You? (DC Comics).
It is quite possible Ebenezer Shark's boathouse that was shown in the 5th episode of Scooby-Doo, Where Are You! is located next to the Coolsville Harbor as the background next to it shows a foggy harbor.