5. Whiscash / ナマズン
They closely resembles the Namazu which is apparent from its Japanese name Namazun. From the pokedex entry,
“As a result of causing tremors by thrashing about, it developed the ability to foretell real earthquakes.”
We could say this corresponds to the legend of the namazu who is a giant catfish that can cause earthquakes. He lives in the mud and would cause earthquakes when it thrashes about. It is believed the origin of the namazu came from observing the sudden activities of catfish when an earthquake is about to happen. Where people from ancient times believed that there must be a giant catfish that was suddenly active and was making all the tremors.