Something Fishy is an episode from Season 2 and is the first appearance of Neptunia.
A day at the beach gets turned upside down when the gang has to deal with attacks from sea creatures. Neptunia appears on a island or sand bank, calling back the creatures from their attacks. Neptunia is sick of the pollution that is dumped in the sea and caused her to mutate. She plans revenge by flooding the city of St. Canard!