In the deep sea of the Great Barrier Reef of Australia, the clownfish father Marlin and his son Nemo live a simple and happy life. However, his father is always timid and a coward. Nemo thinks his father is not brave and even looks down on his father. Little Nemo is fearless. When he went to play on the water with his companions, he was caught by a fishing net and sold to a dentist's clinic. Marlin was very worried about his son's life and death. Even if he couldn't act boldly at ordinary times, he had to be brave for his son. But he encountered many difficulties and fears on the road, which made him very timid. Fortunately, he met the kind-hearted Dori, who accompanied him all the way. Both father and son encountered a lot of enthusiastic help and were able to reunite in the end. Marlin has since become a hero in the hearts of his son and everyone.