Neptuna has lost her memory and Obo doesn't have a cure! A fish tells them that seahorses can cure numerous illnesses. What luck, there are seahorses about - all they have to do is catch one! But what if the fish was wrong?
Ponto is sure that today Balty will meet the mammal of his life. While looking for her the Hydronauts meet many marine animals, but not a single mammal. Watch out for the tide - it's coming in very fast and could be very dangerous!