I wasn't so keen on watching this Scooby adventure as it has the shortest running time of all of them so far and I figured that it couldn't possibly have a substantial mystery worth taking an interest in.
And while that's true for the most part, they do make a huge effort to keep the viewer guessing by throwing in lots of distractions, more so than any other Scooby adventure. And despite it's brief running time it does manage pack in a fair amount of characters and guest voices, so in a sense they give more AND less.
The Mystery Inc. gang head off on a tropical cruise for Fred's birthday but things turn sinister when they pick-up a drifter floating in the water. No one believes his tale of ghost pirates (they're on a "mystery cruise" and are becoming quite jaded to the novelty), but only when said pirates show up do they gradually accept that it's real.
There's a few more in-jokes than normal in this one too. And while I usually hate in-jokes it's forgivable, and perhaps welcome, in a Scooby-Doo mystery. I am aware that the infamous Bermuda Triangle was the focus of a lower-wattage mystery in the third season of Scooby-Doo back in the early 70s, but this one is considerably better.
It looses points for being short, but it's still a worthy mystery.