The whales seduce each other by singing. But our heroes are there to help him compose his song. And when Barnaby and his girl end up beached, Neptuna and her friends come to their rescue once again.

The Hydronauts meet Corky, a killer whale. But Corky is not like all the others. He once lived in an amusement park and does not know how to survive on his own. Neptuna and her crew try to help him rediscover his instincts… at their own danger!

Because the ice is melting and hunting is difficult, Albert the polar bear and come to look for food on board the Hydronica. He scares the crew. But when it comes to saving a mother whale and her baby, Neptuna and the Hydronauts team up with the knowledgeable bear.

The coral are preparing for a mysterious event. All would be going well if Ponto was not having such a run of bad luck. Whatever he does, he does something stupid and upsets the coral. Neptuna and Balty try to convince him that bad luck does not exist. But above all they must correct his mistakes.

It is not only Ponto and Balty who like playing hide and seek. Some little marine animals hide under driftwood to protect themselves from predators. When Balty tries to follow their example, he hides with other fish under a piece of wood that is not drifting. The refuge becomes a trap. Will Ponto find Balty in time to help him?

The Hydronauts want to watch the right whales. But they are hiding, scared by too many gulls in the area. How can the whales and gulls be reconciled? Ask Ponto, he is a gull after all…

Dolphins live as a group so that they can better protect their young from the dangers of the sea. Not only do they protect their young, they can also come to Ponto’s rescue! But the dolphins will also need the Hydronauts’ help…

Balty is determined he has seen a ghost. On board, nobody believes him, especially not Ponto! Everybody knows there’s no such thing as ghosts! But what if Balty really did see something at the bottom of the ocean?

Ponto and Balty are fighting, they each want their own space. A bit like the crocodiles… While Neptuna helps Jonas the crocodile find a new territory, Balty meets Odile, a mother crocodile who needs his help…

The Hydronauts meet Otto, the ranger in an enormous forest of seaweed. But Otto looks after the forest on his own. It’s far too much work! Neptuna and her crew set off to find some female otters to help Otto and save the forest. But the female otters are rather demanding and difficult to please.

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… but watch out for the tide, it’s coming in very fast and could be very dangerous!

Neptuna has lost her memory. Obo does not have a single remedy for her. A fish tells them that seahorses can cure numerous illnesses. What luck, there are seahorses living in this part of the sea. All they have to do is catch one! But what if the fish was wrong?

Balty is sure of what he has heard: Neptuna wants to return to her planet without telling them! When Ponto thinks he has seen another spaceship, he is convinced that Neptuna's friends are coming to find her! Now is the time to act. Disguised as aliens, Ponto and Balty meet manta rays and a remora fish!