A glowing, ghostly diver and string of boat disappearances catches the gang's attention.
This episode includes examples of the following tropes:
- Beneath Suspicion: When pulling off the mask, the gang assumes it's the helpful Mr. Shark pretending to be Captain Cutler's ghost, but instead it's the actual Captain Cutler, whom they'd never before met. (Shaggy, Scooby, and Velma saw a picture of Cutler on his widow's wall earlier, and it was Shaggy who caught on to who he was.)
- Casting Gag: Jean Vander Pyl does a variation of her Winsome Witch voice for Widow Cutler, who claims to practice witchcraft.
- Creepy Old-Fashioned Diving Suit: The ghost of Captain Cutler wears a light-green deep-sea diving suit covered by seaweed in order to steal the yachts of the region. Its distinctiveness, plus its status as one of the first monsters the Mystery Gang investigated, ensured the costume made several other appearances and cameos throughout the franchise.
- Derelict Graveyard: The aptly named Graveyard of Ships.
- Didn't Think This Through: Shaggy and Scooby are underwater (with scuba gear, of course) trying to ward off the ghostly sea diver (the ghost of Captain Cutler) with a cannon on the deck of a sunken ship. Shaggy tries to ignite the cannon's fuse with a match, then remembers matches don't light underwater.
- Digital Destruction: The episode was released on "Scooby-Doo's Greatest Mysteries", but the scene where Shaggy was hopping inside the umbrella was altered as it uses another print due to the lower framerates. Thankfully this was fixed in later releases.
- Early-Installment Weirdness:
- Unlike later installments, the team doesn’t know who the villain of the episode is, because they have never seen his face before.
- Unusually, Shaggy figures out who the captured culprit is, while Velma is mostly irrelevant. After the above example, although the man is clean-shaven, Shaggy has the idea to place seaweed on his face, showing that the guy is Captain Cutler, who faked his death. Shaggy recognized him from a bearded portrait of a younger Cutler, which he had seen earlier that day. In most later episodes, unmasking and recognizing the villain is Velma's main task.
- Faking the Dead: The ghost of Capt. Cutler is actually the still living Captain Cutler.
- Monster of the Week: The Ghost of Captain Cutler.
- Shout-Out: Velma's opinion of a "Witchcraft Made Easy" book is Arte Johnson's catchphrase, "Veeeeerrrrrrry eeenteresting!"
- Stranger Behind the Mask: Played With. The gang captures a ghostly diver and unmasks him but have no idea who he is. However, then Shaggy remembers seeing his picture earlier and recognizes that it's actually the seemingly deceased diver all along pretending to be his own ghost.
- Vile Villain, Saccharine Show: Scooby-Doo is pretty light-hearted, but Captain Cutler's ghost shows a willingness to let Fred, Velma, and Daphne drown when he locks them in an underwater storage unit.
- Wicked Witch: Widow Cutler poses as one, claiming her witchcraft summoned her husband's ghost from the grave. The fact that he's not even dead should be the first clue it's all an act, though.
- Widow Witch: Widow Cutler claims to have summoned the ghost of her dead husband with her magic.
