While visiting the seaside, the gang meets Sonny & Cher, who got stranded on their way to a hotel on Shark Island. The gang gives them a lift, only to end up stuck on the island, which is being menaced by a shark demon.
This episode contains examples of:
- Bitch in Sheep's Clothing: Milo Meekly comes across as a jovial, half-deaf hotel manager who tries hard to accommodate his guests despite the building's poor shape. He also tells them about the legend of the shark demon while dismissing it as a silly legend. In fact, he's behind the "Scooby-Doo" Hoax and makes an effort to hurt or kill the gang once they find out where he's keeping the treasure he doesn't want the IRS to find.
- Borrowed Catchphrase: At the very end, after Sonny makes a humorous remark, Cher responds with Scooby's "Scooby-Dooby Doo!"
- Closed Circle: After their first night at the Hell Hotel, the gang, Sonny & Cher are ready to leave before they find out that the bridge they took to the island is covered by the ocean and it will be about a week before the tide is low enough for them to leave.
- Deadpan Snarker: Cher, often at Sonny's expense.
- Disguised in Drag: The Undercover Cop Reveal features a male cop undercover as a hotel maid.
- False Reassurance: After getting a flat tire, Sonny assures his wife that he didn't forget the jack or the spare tire. Then he admits that he intentionally left the tire behind to make room for his water skis.
- Hell Hotel: The hotel that the main characters visit is filthy, understaffed, sits on the edge of a cliff, and is surrounded by sharks (plus a shark monster). and turned out to have actually been condemned for some time and is in such bad shape that Cher stomping on the porch was enough to send the entire building careening off the cliff
- Meaningless Villain Victory: The villains discover a sunken galleon full of treasure. Even though the treasure is legally theirs, they try to salvage it in secret (with a "Scooby-Doo" Hoax to scare people away) to avoid paying taxes on it. They end up facing attempted murder charges in addition to having to pay at least part of the treasure to the IRS after all.
- The Meddling Kids Are Useless: Judging by how he shows up in the villain's base during the climax, Agent Hidalgo would have solved the case even without the gang's contribution.
- Politically Incorrect Hero: Agent Matt Hidalgo is a brave and competent cop who helps capture the criminals and happily explains everything that's going on to the gang. However, he briefly seems to display a very outdated attitude at the idea that a woman could be an undercover cop.
- Sand Bridge at Low Tide: It's a regular wooden bridge rather than a sand bridge, but the route to Shark Island and its hotel is only accessible for a couple of days a week when the tide is low. Naturally, the hotel guests only discover this once they want to leave.
- Suspicious Spending: Hidalgo figures out that the crooks are illegally salvaging treasure when one of them spends some gold coins in town.
