|This needs a stretch.|
The Haunted Riverboat is a story in Scooby-Doo... Mystery Comics #29
A ghost troubles a riverboat on the Mississippi.
The gang are riding down the Mississippi on the Moonglow, a paddle-wheeler bought by Mr. Hull, Fred's junior high school history teacher. "Skipper" Hull tells them he wouldn't have been able to afford the riverboat, but the Moonglow is supposed to be haunted. In fact, he could only get three men to crew: Hank, Wilson, and Paul. While Shaggy and Fred suit up as crew -- and Daphne and Velma don period dresses -- one of the original crew contacts Spider down in the boiler room of the kids staying on board.
Shortly, Shaggy is assisting the Skipper, while Fred and Scooby stroll the deck. On his transistor radio, Fred hears a newscast, including the lede that a "gangland boss has escaped from prison." Although Fred doesn't appear to realize the significance of this, we assume this gangland boss is Spider. Fred and Scooby hear Velma scream and run to find her in the kitchen, brandishing an iron frying pan at the ghost. Hank and Paul arrive and although the ghost gets away, Scooby tears a piece of the ghost's cloak.
Later, Shaggy is thinking about the fact that Wilson wasn't present when when the ghost appeared and goes to speak with the Skipper. Wilson, in fact, is coming on duty. Shaggy starts to question him, but Wilson points out the ghost right behind Shaggy. The ghost escapes into the river, but Shaggy notices this ghost's cloak isn't ripped. He realizes all three crewman must take turns playing the ghost. Another ghost appears and grabs Scooby, but Velma brains the ghost with her frying pan.
Captured, Hank confesses the three crewman had been smuggling people and things, and had invented the ghost to scare other potential crew away. However, their current "cargo" has fled with the third ghost costume and escaped into the Mardi Gras crowds. The gang takes the remaining two masks with them and, after questioning some Mardi Gras-goers, they track down and capture the escaped convict.