Oggy and the Mermaid is the 73rd episode of Season 4.
Jack is relaxing in the boat while Oggy is scuba diving failing to take pictures of sea life and encounters a mermaid and also a shark. Joey is interested in the mermaid so he decides to kidnap her for his fashion show to make money while his pals are trying to distract the shark. However, Joey's plan has gone too far so Marky and Dee Dee have to get help from the shark and Oggy to foil Joey's plan and rescue the mermaid.
It starts with Oggy goes scuba diving, he wants Jack to go with him. But Jack disagrees and rests in the boat. Oggy will go by himself. He dives but the dive suit's bottom is sticks to the boat's nail, tearing Oggy's suit. Then Oggy swims down to a coral. He takes pictures of it's tentacles but it's quickly avoids Oggy. Oggy is disappointed because his pictures of coral are all holes, so he erases it. But he sees a tortoise, and follows it.
Then, the Cockroaches appear, wearing their swimsuits and jump to the water. They see a gold fish, they laugh at it, the gold fish ignores their laugh and swims away. Then Dee Dee eats the fish, it swims back and says Dee Dee is crazy.
Back at Oggy, the tortoise tricks him to go into a sink boat but while doing so Oggy accidentally finds a mermaid singing so he tries to takes pictures of her but manages to evade him. Oggy then encounters an angry,muscular shark who turns to be the mermaid's Girlfriend. Oggy is then beaten afterwards. The cockroaches have a sea race so Joey rides a seahorse, but he starts getting angry because his brothers are going faster than him, Dee Dee goes with a jellyfish and Marky goes with a ray. When they turn right to the coral, Dee Dee accidentally hits a column, making Joey and Marky laugh. They see the mermaid and the shark playing table tennis, Joey thinks he can kidnap her and make a lot of money. But Dee Dee and Marky disagree with Joey's plan, fearful of the shark noticing and beating them up. Joey thinks again and smiles.
They hide in a shell. Joey says Dee Dee will distract the shark to beat up Oggy, he and Marky will kidnap the mermaid. But Dee Dee fearfully disagrees because he gonna be smashed. Angered, Joey slaps him, prompting DeeDee to finally go. Marky laughs but also gets slapped too. Dee Dee waves the shark's attention and gets squeezed after that. He points out to the shark that Joey and Marky found the mermaid's scout, Oggy. They open Oggy's camouflage and is chased by the shark. Joey & Marky laugh at Dee Dee but he sees the mermaid as a sushi dish, so he tries to eat her but is again slapped by Joey, only managing to get a scale. Joey & Marky then go to the sink boat and kidnap the Mermaid ,leaving DeeDee behind. Wanting revenge, Dee Dee calls the shark, while getting squeezed in the process. He shows the shark that his mermaid friend is missing so he frantically tries to look for her but fails, so he cries. But the paddle (flounder), a Ping-Pong ball (sea urchin) and Dee Dee show the shark where Joey and Marky are. The Shark angrily destroys the boat windows. Hearing the commotion , Marky opens the window and sees the shark heading their way. Shocked and scared he tells that Joey and him will be smashed. Worried, he frantically looks for a way to stop the Shark. He then sees an anchor and smiles having an idea: Marky will sacrifice himself to lure the shark and Joey will anchor the Shark. But Marky fearfully disagrees. He is beaten by Joey and he lures the Shark to the anchor. The shark smashes Marky. Marky points at the anchor, where's Joey pull it down and lands in the Shark's head. Then Joey carries the mermaid away but Oggy stops him. Joey grabs a swordfish and fights Oggy, but Oggy clicks the camera's button, stretching the scope right into Joey's face, with Joey losing all his teeth and collapses. Marky and Dee Dee cheer for Oggy. The Shark takes pictures of Oggy and the mermaid with Marky, Dee Dee, the flounder and the urchin. The last picture is the mermaid kisses Oggy in the cheek. Jack is surprised, he presses the switch rapidly, but he accidentally presses the erase button. Oggy gets angry and chases Jack. In the shore, Marky and Dee Dee wave to good bye the flounder and the urchin, (Joey appears at wounded, his body is float). Seeing Oggy chases Jack, they laugh.
What happens in the story is way similar to the show Zig & Sharko, also created by the episode's writer, Olivier-Jean Marie, and produced by Xilam.