The Black Pearl Mystery is a 1950 Mickey Mouse comic book story, originally published in Four Color Comics #296.
Mickey and Goofy are vacationing on Shark Bay, where they are being watched by an old hermit, who is really Black Pete in disguise. While relaxing on the beach, the two friends are hit by a rolling wave, and Goofy it hit in the head with a bottle. Mickey breaks open the bottle and finds a map inside, and the two row out to their boat to study it. Mickey discovers that the map leads to a sunken treasure and, after noticing that his surroundings match the map's clues, concludes that the boat is right above it.
Later that night, Pete tries to sneak onto the boat to peek at their map. Upon hearing Mickey coming, he dons his hermit disguise. Mickey wards him off, and he tells Goofy to keep their a secret. The next day, the two prepare to dive for the treasure, with Goofy going under and Mickey pumping air. While diving, Goofy is snapped by a crab and attacked by a mischevous octopus. The octopus steals his diving helmet and makes his way up onto the boat. Mickey dives down to rescue Goofy and drives the octopus back into the sea.
Mickey decides to go down and search himself, with Goofy pumping his air, and he comes across a sunken ship. While searching the ship, he finda a strongbox containing a single black pearl. As he tries to exit the ship, Mickey sees that a shark has followed him and is waiting outside to attack. Noticing a barrel full of old salt pork, he decides to feed the shark while me makes his way back to his boat.
Back on the boat, the disguised Pete rows up to visit Goofy and drops his anchor next to it, hitting Mickey on the head. Upon finding out that Mickey found the treasure, Pete reveals himself and orders Goofy at gunpoint to send down a bucket for Mickey to put the pearl in and reel it back up. As Mickey, unaware of what's happening above, puts the pearl in the bucket, he notices he's down to the last piece of salt pork. To drive away the shark, Mickey baits Pete's anchor with the pork, and just as Pete prepares to cut Mickey's air tube, the shark swims away with the anchor and pulls him all the way to China.
Goofy pulls up the bucket and, believing the "little ole black bean" to he worthless, tosses the pearl back into the sea. After Mickey comes back aboard and asks him where the valuble black pearl is, a flustered Goofy tells him that he "dropped somepin'" promptly jumps back into the sea to retrieve it.