The Landonauts and the Rainbow Cloud: Book One by Margaret M Ford

An oil slick appears on the surface of the lake. At first, the lake dwellers mistake it for a rainbow cloud because of all the delightful colours reflected by the sun. Very soon, though, some of the fish begin to get sick, and they realise they must get rid of it quickly. They need to protect their home. But how? Five very brave catfish team up to solve this difficult, scary problem. Before long, they come up with a clever plan. But to reach their goal, they need to be able to walk and breathe on land. How can they possibly do this? Join The Landonauts: Captain Chip, Wagger, Spike, Buttercup and Daisy on their first adventure on land to save and protect their home environment.