Salmon really are surprising fish! They travel up rivers to lay their eggs where they were born. They find their way by tasting the water. But the salmon are lost: the water’s taste has been changed by chemical products. Who has put detergent in the water? How can the salmon be helped? Over to Neptuna and her crew to help the salmons find their way!

Balty is caught in a drift net. How can he free himself? “Wait until the net floats up to the surface” advise the fish. But Balty can’t wait that long, he’s running out of air! Let’s hope Neptuna and Ponto arrive in time to save him…

Obo the computer is not working: Balty and Ponto have emptied the fresh water tanks on board the Hydronica while playing. And without Obo, the voyage cannot continue. Our friends try everything to repair him. But, there is no lack of salt water on this blue planet, fresh water is much rarer…

Rudy the young porpoise has lost his mother. He has tried calling her, she cannot hear him over the noise of the boats. Luckily our heroes are there to help him. Especially when he has to get out of a danger zone, a shipping lane full of enormous cargo ships

The crew of the Hydronica are confronted with an oil slick: the birds can’t fly anymore, the starfish can’t breathe… the oil must be stopped from spreading quickly. And to do it, Ponto and Balty are ready to do anything.

Paul the emperor penguin needs the Hydronauts help. He is injured and cannot take care of his egg any more. A father who incubates eggs? Ponto is amazed. Yes, that’s how the emperor penguins do it! It is a difficult job for our heroes as keeping an egg warm on the ice floe is far from easy…