From the text 'Mijbil the Otter', we learn that otters are intelligent, playful, and curious animals. They naturally enjoy water and are skilled swimmers. Otters are also depicted as affectionate and capable of forming strong bonds with humans. They show a propensity for inventing games and exploring their surroundings. Mij, the otter in the story, exhibits emotions, possesses unique habits, and requires attention and companionship, indicating that otters are sensitive and social creatures.