The third Winx Club movie and sequel to Magical Adventure, taking place between Seasons 5 and 6. This movie was televised or direct-to-video in most countries.
- Audience Participation: The original title of the film (Il mistero degli abissi) (The Mystery of the Abyss) was chosen through an audience poll on the Italian Winx website. The other options were Missione Sirenix (Mission Sirenix), Missione Oceano Infinito (Mission Infinite Ocean), and La magia degli abissi (The Magic of the Abyss).
- The Bus Came Back: After a brief appearance in "The Shark's Eye" in season 5, Politea comes back as this movie's Big Bad.
- Dance Party Ending: The movie ends with all the characters singing and dancing to "We Are All Winx", even Tritannus and the Trix.
- Series Continuity Error: The movie is set between Seasons 5 and 6, but the Winx are shown in their base outfits for the latter season, which they don't receive until Episode 602.
