Fed up with their failures, General Durahan sends out his Shelly Gabus to deal with the gang. The Gabus caught up with the gang who found themselves on a deserted sea platform. After an intense battle, the Mystery Disc dropped into the ocean.
As Mocchi and Genki searched, they encounter Professor Garnish's submarine. Garnish thought they are after his dream treasure (which is actually some sunken treasure of a pirate ship) and chased them away with his cannon. The gang came back after realizing that the only way to get the Mystery Disc back is to make peace and get Garnish to let them use the submarine.
The professor is touched by Holly and decided to help them but not before they kept their side of the bargain which is to do anything for him (i.e. cleaning, cooking...)! Finally the professor, Genki and Mocchi departed. They found the Mystery Disc in an underwater cave which happens to contain the pirates' treasure! Just then, the Gabus attacked!
Can they successfully bring back the Mystery Disc and what will happen to the pirates' treasure?