The Backyardigans (2004)

S3E11 The Great Dolphin Race

Title: The Spectacular Dolphin Derby Plot: In the submerged city of Atlantis, Uniqua aspires to become a champion dolphin racer. When she saves a wild dolphin trapped in a massive clam, she decides to adopt it as her partner. Seeking to improve her skills, Uniqua enlists Pablo's assistance in their training efforts, motivated by her goal to outperform Tyrone, the reigning champion of dolphin racing.